Method and apparatus for transmitting or receiving control channel in communication system

ABSTRACT

A method and apparatus for transmitting or receiving a control channel in a communication system. A method for transmitting control information by a base station includes: configuring a control resource set including a plurality of REGs; interleaving, on a frequency axis, the plurality of REGs included in the control resource set; configuring an REG pool including at least two interleaved REGs; configuring at least one CCE in the REG pool; and transmitting control information through a search space configured by the at least one CCE. Therefore, the present invention improves performance of a communication system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 16/310,162, filed Dec. 14, 2018, which is a U.S. National Phaseentry from International Application No. PCT/KR2018/000219, filed Jan.5, 2018, which claims priority to Korean Patent Application Nos.10-2017-0002557, filed Jan. 6, 2017, 10-2017-0016430, filed Feb. 6,2017, 10-2017-0019629, filed Feb. 13, 2017, 10-2017-0075102, filed Jun.14, 2017, 10-2017-0101401, filed Aug. 10, 2017, 10-2017-0137758, filedOct. 23, 2017, and 10-2018-0001365, filed Jan. 4, 2018, the disclosuresof which are incorporated by reference herein in their entireties.

BACKGROUND 1. Technical Field

The present invention relates to techniques for transmitting andreceiving control channels in a communication system, and moreparticularly, to techniques for configuring, transmitting, and receivingdownlink control channels.

2. Description of Related Art

A communication system (e.g., a ‘new radio (NR)’) using a higherfrequency band (e.g., a frequency band of 6 GHz or higher) than afrequency band (e.g., a frequency band of 6 GHz or lower) of a long termevolution (LTE) based communication system (or, a LTE-A basedcommunication system) is being considered for processing of soaringwireless data. The NR can support not only the 6 GHz or higher frequencyband but also the 6 GHz or lower frequency band, and can support variouscommunication services and scenarios compared to the LTE. Also, therequirements of the NR may include an enhanced mobile broadBand (eMBB),an ultra reliable low latency communication (URLLC), a massive machinetype communication (mMTC), and the like.

Meanwhile, a new transmission scheme for the communication system suchas the NR, which supports a wide frequency band and a wide range ofservices, is required, and in particular, a downlink control channelconfiguration method, a downlink control channel transmission andreception method, and the like are required for stably maintaining aradio link quality.

SUMMARY

In order to solve the above-described problem, the present invention isdirected to providing a method and an apparatus for transmitting andreceiving downlink control channels in a communication system.

A control information transmission method performed in a base station,according to a first embodiment of the present invention for achievingthe above-described objective, may comprise configuring a controlresource set including a plurality of resource element groups (REGs);interleaving the plurality of REGs included in the control resource setin a frequency domain; configuring an REG pool including at least two ofthe interleaved REGs; configuring at least one control channel element(CCE) in the REG pool; and transmitting control information through asearch space composed of the at least one CCE.

Here, each of the plurality of REGs may comprise 12 subcarriers and 1orthogonal frequency division multiplexing (OFDM) symbol.

Here, information on a time-frequency resource in which the controlresource set is configured may be transmitted to a terminal through asignaling procedure.

Here, the control resource set may be a base control resource set or anadditional control resource set, the base control resource set beingused for transmitting control information needed for an initial accessprocedure, and the additional control resource set being used fortransmitting control information needed for a terminal in a radioresource control (RRC) connected state.

Here, the base control resource set may be configured within a minimumsystem bandwidth, and the additional control resource set may beconfigured within an entire system bandwidth.

Here, an index of each of the at least two of the interleaved REGsincluded in the REG pool may be translated to a global index which isunique in the REG pool.

Here, the CCE may include REGs having consecutive global indexes.

Here, the search space may be classified into a common search space anda terminal-specific search space, the common search space being used forall terminals belonging to a coverage of the base station, and theterminal-specific search space being used for a specific terminal amongterminals belonging to the coverage of the base station.

Here, when two CCEs are configured within the REG pool, one of the twoCCEs may be used as the common search space, and the other of the twoCCEs may be used as the terminal-specific search space.

Here, a physical downlink common control channel (PDCCCH) used fortransmitting a common downlink control information (DCI) may beconfigured in the control resource set, and the PDCCCH may be configurednot to overlap with the search space.

Here, a preconfigured region in the control resource set may be used fora data channel, and scheduling information for the data channel may betransmitted through the search space.

A control information reception method performed in a terminal,according to a second embodiment of the present invention for achievingthe above-described objective, may comprise receiving configurationinformation of a control resource set including a plurality of resourceelement groups (REGs) from a base station; identifying a search space inthe control resource set based on the configuration information; andreceiving control information from the base station by performingmonitoring on the search space, wherein the plurality of REGs includedin the control resource set are interleaved on a frequency domain, anREG pool is configured to include at least two of the interleaved REGs,and the search space includes at least one control channel element (CCE)configured in the REG pool.

Here, the control resource set may be a base control resource set or anadditional control resource set, the base control resource set beingused for transmitting control information needed for an initial accessprocedure, and the additional control resource set being used fortransmitting control information needed for a terminal in a radioresource control (RRC) connected state.

Here, the search space may be classified into a common search space anda terminal-specific search space, the common search space being used forall terminals belonging to a coverage of the base station, and theterminal-specific search space being used for a specific terminal amongterminals belonging to the coverage of the base station.

Here, a physical downlink common control channel (PDCCCH) used fortransmitting a common downlink control information (DCI) may beconfigured in the control resource set, and the PDCCCH may be configurednot to overlap with the search space.

Here, a preconfigured region in the control resource set may be used fora data channel, and scheduling information for the data channel may betransmitted through the search space.

A base station for transmitting control information, according to athird embodiment of the present invention for achieving theabove-described objective, may comprise a processor and a memory storingat least one instruction executed by the processor, and the at least oneinstruction may be configured to configure a control resource setincluding a plurality of resource element groups (REGs); interleave theplurality of REGs included in the control resource set in a frequencydomain; configure an REG pool including at least two of the interleavedREGs; configure at least one control channel element (CCE) in the REGpool; and transmit control information through a search space composedof the at least one CCE.

Here, the control resource set may be a base control resource set or anadditional control resource set, the base control resource set beingused for transmitting control information needed for an initial accessprocedure, and the additional control resource set being used fortransmitting control information needed for a terminal in a radioresource control (RRC) connected state.

Here, an index of each of the at least two of the interleaved REGsincluded in the REG pool may be translated to a global index which isunique in the REG pool.

Here, a physical downlink common control channel (PDCCCH) used fortransmitting a common downlink control information (DCI) may beconfigured in the control resource set, and the PDCCCH may be configurednot to overlap with the search space.

Advantageous Effects

According to the present invention, the downlink control channel for thecommunication system can be efficiently configured. That is, when thedownlink control channel is configured according to the embodiments ofthe present invention, the efficiency of resources can be improved, thetransmission capacity of the downlink control channel can be increased,and the reception performance of the downlink control channel can beimproved. Therefore, the performance of the communication system can beimproved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating a first embodiment of acommunication system;

FIG. 2 is a block diagram illustrating a first embodiment of acommunication node constituting a communication system;

FIG. 3 is a conceptual diagram illustrating a first embodiment of acontrol resource set;

FIG. 4A is a conceptual diagram illustrating a first embodiment of a REGpool in a control resource set;

FIG. 4B is a conceptual diagram illustrating a second embodiment of aREG pool in a control resource set;

FIG. 4C is a conceptual diagram illustrating a third embodiment of a REGpool in a control resource set;

FIG. 4D is a conceptual diagram illustrating a fourth embodiment of aREG pool in a control resource set;

FIG. 4E is a conceptual diagram illustrating a fifth embodiment of a REGpool in a control resource set;

FIG. 5 is a conceptual diagram illustrating a first embodiment of aCCE-REG mapping scheme;

FIG. 6 is a conceptual diagram illustrating a first embodiment of asearch space configured in an REG pool;

FIG. 7 is a conceptual diagram illustrating a second embodiment of asearch space configured in an REG pool;

FIG. 8 is a conceptual diagram illustrating a third embodiment of asearch space configured in an REG pool;

FIG. 9A is a conceptual diagram illustrating a first embodiment of asearch space in a control resource set;

FIG. 9B is a conceptual diagram illustrating a second embodiment of asearch space in a control resource set;

FIG. 9C is a conceptual diagram illustrating a third embodiment of asearch space in a control resource set;

FIG. 10A is a conceptual diagram illustrating a first embodiment of CCEsaccording to a localized CCE-REG mapping;

FIG. 10B is a conceptual diagram illustrating a second embodiment ofCCEs according to a localized CCE-REG mapping;

FIG. 10C is a conceptual diagram illustrating a third embodiment of CCEsaccording to a localized CCE-REG mapping;

FIG. 11A is a conceptual diagram illustrating a first embodiment of amethod of configuring a search space and a PDCCCH;

FIG. 11B is a conceptual diagram illustrating a second embodiment of amethod of configuring a search space and a PDCCCH;

FIG. 11C is a conceptual diagram illustrating a third embodiment of amethod of configuring a search space and a PDCCCH;

FIG. 11D is a conceptual diagram illustrating a fourth embodiment of amethod of configuring a search space and a PDCCCH;

FIG. 12 is a conceptual diagram illustrating a first embodiment of amethod of configuring a data region and a control region;

FIG. 13A is a conceptual diagram illustrating a first embodiment of agap configured in a control region;

FIG. 13B is a conceptual diagram illustrating a second embodiment of agap configured in a control region;

FIG. 14 is a conceptual diagram illustrating a first embodiment of adata channel scheduling method;

FIG. 15 is a conceptual diagram illustrating a second embodiment of adata channel scheduling method;

FIG. 16 is a conceptual diagram illustrating a third embodiment of adata channel scheduling method;

FIG. 17 is a conceptual diagram illustrating a fourth embodiment of adata channel scheduling method;

FIG. 18 is a conceptual diagram illustrating a first embodiment of ascheduling method in a multi-beam scenario;

FIG. 19 is a conceptual diagram illustrating a first embodiment of abeamforming transmission method; and

FIG. 20 is a conceptual diagram illustrating a second embodiment of abeamforming transmission method.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible to various modifications andalternative forms, specific embodiments are shown by way of example inthe drawings and described in detail. It should be understood, however,that the description is not intended to limit the present invention tothe specific embodiments, but, on the contrary, the present invention isto cover all modifications, equivalents, and alternatives that fallwithin the spirit and scope of the present invention.

Although the terms “first,” “second,” etc. may be used herein inreference to various elements, such elements should not be construed aslimited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and a second element could be termed a first element,without departing from the scope of the present invention. The term“and/or” includes any and all combinations of one or more of theassociated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directed coupled” to another element, there are nointervening elements.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of embodiments ofthe present invention. As used herein, the singular forms “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises,” “comprising,” “includes,” and/or “including,”when used herein, specify the presence of stated features, integers,steps, operations, elements, parts, and/or combinations thereof, but donot preclude the presence or addition of one or more other features,integers, steps, operations, elements, parts, and/or combinationsthereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by thoseof ordinary skill in the art to which the present invention pertains. Itwill be further understood that terms defined in commonly useddictionaries should be interpreted as having a meaning that isconsistent with their meaning in the context of the related art and willnot be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.To facilitate overall understanding of the present invention, likenumbers refer to like elements throughout the description of thedrawings, and description of the same component will not be reiterated.

A communication system to which embodiments of the present disclosureare applied will be described. The communication system may be the 4Gcommunication system (e.g., the long-term evolution (LTE) communicationsystem, the LTE-Advance (LTE-A) communication system, or the like), the5G communication system (e.g. the NR communication system), or the like.The 4G communication system may support communications in a frequencyband of 6 GHz or below, and the 5G communication system may supportcommunications in a frequency band of 6 GHz or above as well as thefrequency band of 6 GHz or below. The communication systems to which theembodiments according to the present disclosure are applied are notrestricted to what will be described below, and the embodimentsaccording to the present disclosure may be applied to variouscommunication systems. Here, the term ‘communication system’ may be usedwith the same meaning as the term ‘communication network’.

FIG. 1 is a conceptual diagram illustrating a first embodiment of acommunication system.

Referring to FIG. 1, a communication system 100 may comprise a pluralityof communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2,130-3, 130-4, 130-5, and 130-6. Also, the communication system 100 mayfurther include a core network (e.g., a serving gateway (S-GW), a packetdata network (PDN) gateway (P-GW), a mobility management entity (MME),or the like).

The plurality of communication nodes may support 4th generation (4G)communication (e.g., long term evolution (LTE), LTE-advanced (LTE-A)),5th generation (5G) communication, or the like. The 4G communication maybe performed in a frequency band below 6 gigahertz (GHz), and the 5Gcommunication may be performed in a frequency band above 6 GHz. Forexample, for the 4G and 5G communications, the plurality ofcommunication nodes may support at least one communication protocolamong a code division multiple access (CDMA) based communicationprotocol, a wideband CDMA (WCDMA) based communication protocol, a timedivision multiple access (TDMA) based communication protocol, afrequency division multiple access (FDMA) based communication protocol,an orthogonal frequency division multiplexing (OFDM) based communicationprotocol, an orthogonal frequency division multiple access (OFDMA) basedcommunication protocol, a cyclic prefix OFDM (CP-OFDM) basedcommunication protocol, a discrete Fourier transform spread OFDM(DFT-s-OFDM) based communication protocol, a single carrier FDMA(SC-FDMA) based communication protocol, a non-orthogonal multiple access(NOMA) based communication protocol, a generalized frequency divisionmultiplexing (GFDM) based communication protocol, a filter bankmulti-carrier (FBMC) based communication protocol, a universal filteredmulti-carrier (UFMC) based communication protocol, and a space divisionmultiple access (SDMA) based communication protocol. Each of theplurality of communication nodes may have the following structure.

FIG. 2 is a block diagram illustrating a first embodiment of acommunication node constituting a cellular communication system.

Referring to FIG. 2, a communication node 200 may comprise at least oneprocessor 210, a memory 220, and a transceiver 230 connected to thenetwork for performing communications. Also, the communication node 200may further comprise an input interface device 240, an output interfacedevice 250, a storage device 260, and the like. Each component includedin the communication node 200 may communicate with each other asconnected through a bus 270.

The processor 210 may execute a program stored in at least one of thememory 220 and the storage device 260. The processor 210 may refer to acentral processing unit (CPU), a graphics processing unit (GPU), or adedicated processor on which methods in accordance with embodiments ofthe present disclosure are performed. Each of the memory 220 and thestorage device 260 may be constituted by at least one of a volatilestorage medium and a non-volatile storage medium. For example, thememory 220 may comprise at least one of read-only memory (ROM) andrandom access memory (RAM).

Referring again to FIG. 1, the communication system 100 may comprise aplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and aplurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6.Each of the first base station 110-1, the second base station 110-2, andthe third base station 110-3 may form a macro cell, and each of thefourth base station 120-1 and the fifth base station 120-2 may form asmall cell. The fourth base station 120-1, the third terminal 130-3, andthe fourth terminal 130-4 may belong to cell coverage of the first basestation 110-1. Also, the second terminal 130-2, the fourth terminal130-4, and the fifth terminal 130-5 may belong to cell coverage of thesecond base station 110-2. Also, the fifth base station 120-2, thefourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal130-6 may belong to cell coverage of the third base station 110-3. Also,the first terminal 130-1 may belong to cell coverage of the fourth basestation 120-1, and the sixth terminal 130-6 may belong to cell coverageof the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2 may refer to a Node-B, a evolved Node-B (eNB), a gNB, anng-eNB, a high reliability base station (HR-BS), a base transceiverstation (BTS), a radio base station, a radio transceiver, an accesspoint, an access node, a radio access station (RAS), a mobile multi-hoprelay base station (MMR-BS), a relay station (RS), an advanced relaystation (ARS), a high reliability relay station (HR-RS), a home NodeB(HNB), a home eNodeB (HeNB), a road side unit (RSU), a radio remote head(RRH), a transmission point (TP), a transmission and reception point(TRP), or the like.

Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5,and 130-6 may refer to a user equipment (UE), a terminal, an accessterminal, a mobile terminal, a station, a subscriber station, a mobilestation, a portable subscriber station, a node, a device, an on-boardunit (OBU), or the like.

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3,120-1, and 120-2 may operate in the same frequency band or in differentfrequency bands. The plurality of base stations 110-1, 110-2, 110-3,120-1, and 120-2 may be connected to each other via an ideal backhaul ora non-ideal backhaul, and exchange information with each other via theideal or non-ideal backhaul. Also, each of the plurality of basestations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to thecore network through the ideal or non-ideal backhaul. Each of theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 maytransmit a signal received from the core network to the correspondingterminal 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6, and transmit asignal received from the corresponding terminal 130-1, 130-2, 130-3,130-4, 130-5, or 130-6 to the core network.

Also, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2 may support a multi-input multi-output (MIMO) transmission(e.g., a single-user MIMO (SU-MIMO), a multi-user MIMO (MU-MIMO), amassive MIMO, or the like), a coordinated multipoint (CoMP)transmission, a carrier aggregation (CA) transmission, a transmission inunlicensed band, a device-to-device (D2D) communication (or, proximityservices (ProSe)), an Internet of things (IoT) communication, dualconnectivity (DC), or the like. Here, each of the plurality of terminals130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 may perform operationscorresponding to the operations of the plurality of base stations 110-1,110-2, 110-3, 120-1, and 120-2 (i.e., the operations supported by theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2). Forexample, the second base station 110-2 may transmit a signal to thefourth terminal 130-4 in the SU-MIMO manner, and the fourth terminal130-4 may receive the signal from the second base station 110-2 in theSU-MIMO manner. Alternatively, the second base station 110-2 maytransmit a signal to the fourth terminal 130-4 and fifth terminal 130-5in the MU-MIMO manner, and the fourth terminal 130-4 and fifth terminal130-5 may receive the signal from the second base station 110-2 in theMU-MIMO manner.

The first base station 110-1, the second base station 110-2, and thethird base station 110-3 may transmit a signal to the fourth terminal130-4 in the CoMP transmission manner, and the fourth terminal 130-4 mayreceive the signal from the first base station 110-1, the second basestation 110-2, and the third base station 110-3 in the CoMP manner.Also, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2 may exchange signals with the corresponding terminals 130-1,130-2, 130-3, 130-4, 130-5, or 130-6 which belongs to its cell coveragein the CA manner. Each of the base stations 110-1, 110-2, and 110-3 maycontrol D2D communications between the fourth terminal 130-4 and thefifth terminal 130-5, and thus the fourth terminal 130-4 and the fifthterminal 130-5 may perform the D2D communications under control of thesecond base station 110-2 and the third base station 110-3.

Meanwhile, the communication system may support a frequency divisionduplex (FDD) scheme, a time division duplex (TDD) scheme, and the like.Also, the communication system (e.g., NR) may support a variety ofnumerologies (e.g., various waveform parameter sets) as shown in Table 1below. Table 1 may represent numerologies to which normal cyclicprefixes (CPs) defined in the LTE (e.g., the same CP overhead as theLTE) are applied, and when the CP-OFDM is used, each numerology may bedefined with a subcarrier spacing and a CP length. For the purpose ofreducing implementation complexity and effectively supporting operations(e.g., CA operation, DC operation, multiplexing operation ofheterogeneous numerologies in one carrier, and the like), exponentialrelations of 2 may be established between the subcarrier spacings inTable 1.

TABLE 1 Numerology Index #1 #2 #3 #4 #5 #6 Subcarrier spacing 15 kHz 30kHz 60 kHz 120 kHz 240 kHz 480 kHz OFDM symbol length (μs) 66.7 33.316.7 8.3 4.2 2.1 CP length (μs) 4.76 2.38 1.19 0.60 0.30 0.15 The numberof OFDM 14 28 56 112 224 448 symbols in 1 ms

The numerology #1 may be suitable for a scenario where LTE and NR sharethe same frequency band in the same area. The numerology may beselectively used depending on an operation frequency band, a targetservice, a scenario, and the like. Also, a specific numerology may beused for specific signals or for specific channels. For example,numerologies (i.e., numerologies #1 to #3) corresponding to a subcarrierspacing of 60 kHz or less may be used for a frequency band of 6 GHz orless, and numerologies (i.e., numerologies #3 to #6) corresponding to asubcarrier spacing of 60 kHz or higher may be used for a frequency bandof 6 GHz or higher. Also, a numerology (i.e., numerology #1)corresponding to a subcarrier spacing of 15 kHz may be used for anenhanced mobile broadband (eMBB) service, and a numerology (i.e.,numerology #3) corresponding to a subcarrier spacing of 60 kHz may beused for an ultra-reliable low latency communication (URLLC) service.

One numerology may be used for one cell or one carrier. Also, onenumerology may be used for a specific time-frequency resource in onecarrier. The heterogeneous numerologies may be used for differentoperation frequency bands. Also, the heterogeneous numerologies may beused to support different services (or requirements) within the samefrequency band (e.g., the same carrier). A numerology having thesubcarrier spacing smaller than that of the numerology #1 may be used tosupport a massive machine type communication (mMTC) service, amultimedia broadcast multicast service (MBMS) service, or the like. Forexample, a numerology having a subcarrier spacing of 7.5 kHz or 3.75 kHzmay be considered.

On the other hand, a frame structure for the NR may be constituted asfollows. In the NR, a building block on the time domain may include asubframe, a slot, a minislot, an OFDM symbol, and the like. In theembodiments to be described below, an ‘OFDM symbol’ may be replaced witha symbol based on another waveform technology. The length of thesubframe may be 1 ms regardless of the subcarrier spacing. The slot maycomprise 14 consecutive OFDM symbols. Therefore, the length of the slotmay be inversely proportional to the subcarrier spacing, unlike thelength of the subframe.

A control channel (e.g., a downlink control channel and an uplinkcontrol channel) and a data channel (e.g., a downlink data channel andan uplink data channel) may be configured in each of the slots, and thecontrol channel may be disposed in at least one of a front region and arear region of the corresponding slot. In the case that a slot-basedscheduling is used, one slot may be a minimum scheduling unit, and inthis case, the base station may transmit scheduling information to theterminal through a downlink control channel of each of the slots.

The slot type may be classified into a downlink slot including adownlink interval, an uplink slot including an uplink interval, abi-directional slot including a downlink interval and an uplinkinterval, and the like. A guard interval may be located between thedownlink interval and the uplink interval in the bi-directional slot,and the length of the guard interval may be set to be larger than a sumof twice a propagation delay and a delay spread. A plurality of slotsmay be aggregated to transmit one data packet or one transport block(TB). Alternatively, a plurality of slots may be aggregated to transmita plurality of data packets or a plurality of transport blocks.

In the NR, a scheduling based on a minislot with a length shorter thanthe slot may be used. For example, a minislot may be used for supportingan aggressive time division multiplexing (TDM) for analog or hybridbeamforming in a frequency band of 6 GHz or above, partial slottransmission in an unlicensed band, the partial slot transmission in afrequency band where NR and LTE coexist, the URLLC service, and thelike.

In order to support various embodiments, the length and starting point(e.g., position) of the minislot may be flexibly defined. For example,when one slot includes M OFDM symbols, the minislot may be configured toinclude 1 to (M−1) OFDM symbols. Here, M may be an integer of 2 or more.The length and starting point of the minislot may be explicitlyconfigured for the terminal. In this case, the base station may informthe terminal of the length and starting time of the minislot.Alternatively, the minislot-based scheduling may be operated byappropriately setting a monitoring period for the control channel,the-time domain resource size of the scheduled data channel, or the likewithout explicitly configuring the length and the starting time point ofthe minislot in the terminal.

In the LTE, a basic unit of resource allocation may be a physicalresource block (PRB) pair, and one PRB pair may include 2 consecutiveslots in the time domain and 12 consecutive subcarriers in the frequencydomain. On the other hand, in the NR, a PRB may be used as a resourceallocation unit in the frequency domain. In this case, one PRB mayinclude 12 subcarriers regardless of the numerology. Thus, the bandwidthoccupied by one PRB may be proportional to the subcarrier spacing of thenumerology. For example, the bandwidth occupied by one PRB for the caseof using the numerology #3 corresponding to the subcarrier spacing of 60kHz may be four times the bandwidth occupied by one PRB for the case ofusing the numerology #1 corresponding the subcarrier spacing of 15 kHz.

Hereinafter, a method of configuring a downlink control channel, amethod of transmitting and receiving a downlink control channel, amethod of configuring a reference signal for decoding a downlink controlchannel, etc., in the NR will be described. Even when a method (e.g.,transmission or reception of a signal) performed at the firstcommunication node among the communication nodes is described, thecorresponding second communication node may perform a method (e.g.,reception or transmission of the signal) corresponding to the methodperformed at the first communication node. That is, when an operation ofthe terminal is described, the corresponding base station may perform anoperation corresponding to the operation of the terminal. Conversely,when an operation of the base station is described, the correspondingterminal may perform an operation corresponding to the operation of thebase station.

The embodiments described below may be applied to other communicationsystems (e.g., LTE) as well as the NR. In the following embodiments, acontrol channel may indicate at least one of a downlink control channel(e.g., PDCCH) and an uplink control channel (e.g., PUCCH), and a datachannel may indicate at least one of a downlink data channel (e.g.,PDSCH) and an uplink data channel (e.g., PUSCH).

In the NR, a terminal may receive a PDCCH by performing a blind decodingoperation. In this case, the terminal performs the blind decodingoperation on PDCCH candidates (e.g., candidate resource regions throughwhich a PDCCH may be transmitted) in a predefined search space todetermine whether there is a PDCCH for itself, and may receive the PDCCHwhen there is the PDCCH for itself. Here, the search space may bereferred to as a ‘control channel search space’ or a ‘PDCCH searchspace’, and may be a set of the PDCCH candidates. A control channelelement (CCE) may be a minimum resource region in which one PDCCH can betransmitted. One PDCCH may be transmitted through one CCE.Alternatively, one PDCCH may be transmitted via aggregated CCEs. As aCCE aggregation level is higher, one PDCCH may occupy more resourceregions, and in this case, a PDCCH reception performance may be improvedby lowering a coding rate of the PDCCH.

At least one PDCCH candidate may be configured in each of the CCEaggregation levels. For example, in the LTE, the CCE aggregation levelmay be set to 1, 2, 4, 8, or the like, and a fixed number of PDCCHcandidates for each of the CCE aggregation levels may be defined. In theLTE, a common search space (CSS) may be a common search space that allterminals monitor and may support the CCE aggregation levels 4 and 8. Aterminal-specific search space (i.e., UE-specific search space) may be asearch space configured for each terminal and may support the CCEaggregation levels 1, 2, 4, and 8.

In the NR, a basic unit of the downlink control channel may be aresource element group (REG). The REG may be composed of 1 PRB (e.g., 12subcarriers) in the frequency domain and 1 OFDM symbol in the timedomain. Thus, one REG may contain 12 resource elements (REs). The REGmay include REs to which a demodulation reference signal (DMRS) used fordecoding the downlink control channel is mapped. In this case, REs towhich the downlink control channel can be mapped in one REG may be REsother than the REs to which the DMRS is mapped among the 12 REs. One CCEmay include at least one REG. All CCEs may include the same number ofREGs. Alternatively, the CCEs may include a different number of REGs.

Meanwhile, the terminal may receive downlink control information (DCI)through the PDCCH. The DCI may include a common DCI received by aplurality of terminals in common and a terminal-specific (i.e.,UE-specific) DCI received by a specific terminal. For example, thecommon DCI may include resource allocation information for transmissionof system information (SI), power control information, slotconfiguration information (e.g., slot type and slot structure), TDDuplink (UL)/downlink (DL) configuration information, control channelconfiguration information, random access response related information,paging related information, and the like. The UE-specific DCI mayinclude uplink scheduling information, downlink scheduling information,and the like.

In the LTE, the PDCCH resource region may be defined in the entiresystem bandwidth, and the PDCCH may be distributed in the wide frequencyregion through interleaving in the time-frequency domain. On the otherhand, in the NR, for the sake of forward compatibility, a case where aspecific signal or a specific channel is transmitted in the entiresystem bandwidth and a case where a specific signal or a specificchannel is always transmitted periodically may be minimized. Forexample, in the NR, the PDCCH may be transmitted over a specific limitedfrequency band, and when necessary, resources for the PDCCH may beadditionally configured in other frequency bands. That is, in terms ofthe system and the terminal, a plurality of resource regions for thePDCCH may be configured.

Control Resource Set (CORESET)

On the other hand, in the NR, a control resource set may be configured,and the control resource set may include a PDCCH search space (i.e., aresource region on which the terminal performs a blind decodingoperation for the PDCCH). The control resource set may be referred to asa ‘CORESET’. The control resource set may be composed of a plurality ofPRBs in the frequency domain and a plurality of OFDM symbols in the timedomain. As an example, the control resource set may consist of a limitednumber of PRBs in the frequency domain and a limited number of OFDMsymbols in the time domain. As another example, the control resource setmay comprise a limited number of PRBs in the frequency domain and anentire time resource in the time domain (e.g., all OFDM symbols in thetime domain). In this case, configuration information of the controlresource set transmitted to the terminal by the base station may includefrequency domain resource information and may not include time domainresource information.

The control resource set may include a plurality of REGs. The controlresource set may include at least one CCE. The PRBs belonging to onecontrol resource set may be continuous or discontinuous in the frequencydomain. At least one control resource set may be configured for aterminal. When a plurality of control resource sets are configured for aterminal, one DCI may be transmitted in one control resource set.

The control resource sets may be classified into a base control resourceset and an additional control resource set. The base control resourceset may be a resource region which is initially monitored by theterminal performing an initial access procedure in a radio resourcecontrol idle state (i.e., RRC_IDLE state) to receive a PDCCH. Theterminal in an RRC connected state (i.e., RRC_CONNECTED state) as wellas the terminal in the RRC_IDLE state may perform monitoring on the basecontrol resource set. The base control resource set may be configured tothe terminal through system information transmitted through a physicalbroadcast channel (PBCH) or another channel. The additional controlresource set may be configured to the terminal through a signalingprocedure (e.g., an RRC signaling procedure). Therefore, the additionalcontrol resource set may be valid for a terminal in the RRC_CONNECTEDstate and may be configured for a specific terminal.

The base control resource set may be defined within the minimum systembandwidth that is commonly supported by all the terminals performing theinitial access procedure, and the additional control resource set may beconfigured within a frequency band that is wider than the frequency bandto which the base control resource set is allocated. For example, theadditional control resource set may be configured in any frequency bandwithin the bandwidth of the operation frequency of the terminal (e.g., abandwidth part). The operation frequency (e.g., bandwidth part) of theterminal may be configured within the system bandwidth or an RF channelbandwidth of the terminal. At least one base control resource set may beconfigured in a cell or a carrier in a standalone mode in order tosupport the terminal in the RRC_IDLE state. The search space belongingto the base control resource set may be referred to as a ‘base searchspace’, and the search space belonging to the additional controlresource set may be referred to as an ‘additional search space’.

FIG. 3 is a conceptual diagram illustrating a first embodiment of acontrol resource set.

Referring to FIG. 3, a plurality of control resource sets may beconfigured within one carrier (e.g., entire system bandwidth). A firstcontrol resource set may be a base control resource set, and a secondcontrol resource set may be an additional control resource set. Thebandwidth of the first control resource set may be set so as not toexceed the minimum system bandwidth of the terminals described above.

Since the first control resource set and the second control resource setare configured within the bandwidth of the operation frequency of afirst terminal, the first terminal may perform monitoring on at leastone of the first control resource set and the second control resourceset. Since the second control resource set is configured within thebandwidth of the operation frequency of a second terminal, the secondterminal may perform monitoring on the second control resource set.Since the first control resource set is configured within the bandwidthof the operation frequency of a third terminal, the third terminal mayperform monitoring on the first control resource set.

Meanwhile, the common DCI may be transmitted periodically oraperiodically through the base control resource set. In this case, evenafter the initial access procedure is completed, the terminal mayperform monitoring on the base control resource set to receive thecommon DCI. However, a terminal transiting from the RRC_IDLE state tothe RRC_CONNECTED state may operate in a frequency band other than thefrequency band in which the base control resource set is configured. Inthis case, the terminal may retune the operation frequency band at eachmonitoring time of the base control resource set to monitor the basecontrol resource set. Alternatively, the terminal may be configured tohave an additional control resource set for transmission of the commonDCI within its operation frequency band.

Common DCI

The base station may inform the terminal of a transmission cycle of thecommon DCI, a position of a transmission slot of the common DCI (e.g.,slot index), and the like through a signaling procedure (e.g., RRCsignaling procedure). The transmission cycle of the common DCI may beindicated by the number of slots. When the common DCI is not received,the terminal may not be able to successfully perform not only thereception operation of the PDCCH but also other operations. For example,the terminal that has not received the common DCI (e.g., slotconfiguration information) may not receive a PDSCH because it does notknow information on the downlink interval of the slot. Also, theterminal that has not received the common DCI (e.g., slot configurationinformation) may transmit an uplink signal and a channel in a wrongperiod because it does not know information on the uplink interval ofthe slot. In this case, the base station may not receive the uplinksignal and the channel from the terminal.

In order to solve this problem, through a UE-specific DCI, the basestation may inform the terminal of transmission period information of adownlink data channel (e.g., PDSCH), transmission period information ofan uplink data channel (e.g., PUSCH), and the like. Here, thetransmission period information may include a starting symbol index andan ending symbol index of a transmission period, or may include thestarting symbol index and the length of the transmission period. In thiscase, the terminal may receive the downlink data channel in thetransmission period indicated by the UE-specific DCI, and may transmitthe uplink data channel in the transmission period indicated by theUE-specific DCI. Therefore, the problem caused by the reception failureof the common DCI may be solved.

Meanwhile, in the NR, a multi-antenna based beamforming scheme may beused to compensate for a coverage loss due to high signal attenuation inthe high frequency band. In order to transmit common information orbroadcast information to an entire coverage of a cell (or a sector), abeam sweeping scheme may be used in which a plurality of beams aresequentially transmitted in a plurality of time intervals. The beamsweeping scheme may be applied for the transmission of common DCI. In anenvironment where the beamforming scheme (e.g., beam sweeping scheme) isused, the operation of the terminal may be configured not to depend onthe common DCI. For this, an RRC signaling procedure for configuring theslot over which the common DCI is transmitted may be performed if thebase station desires.

The common DCI may be transmitted via a PDCCH or another channel(hereinafter referred to as a ‘physical downlink common control channel(PDCCCH)’). The PDCCCH may be configured to be similar to a physicalcontrol format indicator channel (PCFICH) defined in the LTE. The codingand decoding procedure and the resource structure for the PDCCCH may beconfigured differently from the coding and decoding procedure and theresource structure for the PDCCH, and the PDCCCH may be received from afixed resource without performing the blind decoding operation. Sincethe PDCCCH can be received without performing the blind decodingoperation, a time required for reception of the PDCCCH may be reduced.Configuration information of a slot through which the PDCCCH istransmitted (hereinafter referred to as a ‘PDCCCH slot’) may betransmitted through a system information transmission procedure (e.g.,signaling procedure), and in this case, the terminal in theRRC_CONNECTED state as well as the terminal in the RRC_IDLE state mayreceive the configuration information of the PDCCCH slot.

Meanwhile, when the common DCI is transmitted via the PDCCH (hereinafterreferred to as a ‘PDCCH based common DCI transmission scheme’), theterminal may obtain the common DCI by performing the blind decodingoperation. In this case, in order to reduce the complexity of the blinddecoding operation on the common DCI, the search space for the commonDCI may be limited to some search space (e.g., common search space)among the entire search spaces. Also, the common DCI may be located in afront region of the slot.

In the PDCCH based common DCI transmission scheme, the PDCCCH may not beused. When several types of common DCIs are defined, the number ofcommon DCIs transmitted in one slot may be variable. In this case,various types of common DCIs may be flexibly scheduled through aplurality of PDCCH candidates. Also, the PDCCH based common DCItransmission scheme may provide forward compatibility. Even when a newcommon DCI is introduced in the future, the new common DCI may betransmitted through the same PDCCH (e.g., search space) without furtherdefining a separate channel for transmitting the new common DCI.

Since the PDCCH resource region is shared by the common DCI or otherDCIs, there may be no resource loss even when the base station does nottransmit the corresponding common DCI through the slot through which thecommon DCI is transmitted (or the candidate slot through which thecommon DCI can be transmitted). When the base station does not transmitthe common DCI in the slot or the candidate slot, the terminal mayperform related operations using predefined default information (or,preconfigured default information). Alternatively, the terminal mayperform the related operations using a previously received common DCI.In term of the reception delay or reception complexity, the receptiondelay of the common DCI may be minimized when the search space throughwhich the common DCI is transmitted is placed in the front region of theslot. Also, when a specific common DCI is configured to be transmittedthrough a specific PDCCH candidate (e.g., a set of specific CCEs), thereception complexity may be reduced since the terminal can receive thespecific common DCI without the blind decoding operation.

For example, the specific common DCI may be transmitted through a PDCCHcandidate K of a CCE aggregation level L among PDCCH candidatesconstituting a search space (hereinafter referred to as a ‘Method200-1’). The Method 200-1 may be applied to the slot through which thespecific common DCI is transmitted, and the PDCCH candidate may be usedfor general purposes in the remaining slots. In this case, the specificcommon DCI may include a slot format indicator (SFI) described below(e.g., information indicating a slot format used in the NR).Alternatively, the specific common DCI may be a preemption indicator ofthe NR. Also, the search space for the specific common DCI may be thecommon search space or the UE-specific search space.

On the other hand, the terminal may monitor only the specific common DCIin a dedicated PDCCH candidate in the slot through which the specificcommon DCI is transmitted (or, the candidate slot through which thespecific common DCI can be transmitted) (hereinafter, referred to as a‘Method 200-2’). The base station may be allowed not to transmit thespecific common DCI in the slot (or, candidate slot). According toMethod 200-2, when the base station does not transmit the specificcommon DCI through the dedicated PDCCH candidate, resources of thededicated PDCCH candidate may be wasted. In order to solve this problem,the terminal may monitor not only the specific common DCI but also otherDCIs on the PDCCH candidate (e.g., dedicated PDCCH candidate)(hereinafter referred to as a ‘Method 200-3’). For Methods 200-1 to200-3, the base station may inform the terminal of the positioninformation (e.g., L, K) of the search space for monitoring the commonDCI through a signaling procedure (e.g., RRC signaling procedure).

Information Included in a Common DCI

The common DCI may include slot configuration information (e.g., slotformat indicator). The slot configuration information may includeinformation indicating each of a downlink interval, a guard interval,and an uplink interval of a slot (e.g., position information of OFDMsymbols (e.g., OFDM symbol set) belonging to each of the downlinkinterval, the guard interval, and the uplink interval). The guardinterval may be an unknown interval for which a transmission direction(e.g., uplink or downlink direction) is not defined. The terminal maynot perform transmission and reception operations in the unknowninterval until the transmission direction is determined by overridingthe unknown interval by other signaling.

A transmission cycle of the slot configuration information may be set toN slots. N may be an integer of 1 or more. For coexistence of the NR andthe LTE in the same frequency band, the transmission cycle of the slotconfiguration information may be set to 10 ms, 20 ms, 40 ms, or 80 ms,which is a transmission cycle of reconfiguration information for UL/DLconfiguration in the LTE. When N>1, the slot configuration informationmay be applied to N consecutive slots. When X bits are needed toindicate the structure of one slot, a maximum of ‘N×X’ bits may beneeded to indicate the structures of N slots.

Also, the common DCI may include reserved resource information. Thereserved resource information may be used to indicate that a specifictime-frequency resource is reserved in a slot (or slot group). Theterminal receiving the reserved resource information may determine thata specific signal and a specific channel for itself are not transmittedthrough the time-frequency resource indicated by the reserved resourceinformation (hereinafter referred to as a ‘Method 300-1’).Alternatively, the terminal receiving the reserved resource informationmay determine that no signal or channel for itself is transmittedthrough the time-frequency resource indicated by the reserved resourceinformation (hereinafter referred to as a ‘Method 300-2’).

In Method 300-1, the specific signal may be a signal transmitted over aslot, and the specific channel may be a PDSCH, PUSCH, PUCCH, etc.transmitted over a slot. Also, in Method 300-1, each of the specificsignal and the specific channel may not include a signal and a channeltransmitted through a minislot. In this case, the base station mayreserve a specific time-frequency resource using the common DCI andperform minislot-based transmission using the reserved specifictime-frequency resource. Also, the reserved resource information may beused to protect transmission of downlink and uplink reference signals.For example, the time-frequency resource indicated by the reservedresource information may be used for transmission such as CSI-RS,sounding reference signal (SRS), and the like.

It may be preferable that the information included in the common DCI(e.g., slot configuration information, reserved resource information,etc.) described above is received at the earliest time in the terminalside with minimum complexity. Thus, the information included in thecommon DCI may be transmitted over a limited specific search space(e.g., common search space) within the PDCCCH or PDCCH. The common DCIhaving the features described above may be referred to as a ‘firstcommon DCI’). The first common DCI may be transmitted over a groupcommon PDCCH of the NR. In this case, at least one of a transmissioncycle and a position of a transmission slot of each of the first commonDCIs may be configured independently.

Meanwhile, a common DCI (hereinafter referred to as a ‘second commonDCI’) other than the first common DCI may include information for arandom access response, scheduling information of a PDSCH includingsystem information, power control information, and the like. The secondcommon DCI may be transmitted through a PDCCH. The search space (e.g.,common search space, UE-specific search space) for the second common DCImay be configured to be wider than the search space for the first commonDCI.

Search Space

The search space of LTE may be classified into the common search spaceand the UE-specific search space, and the type of the radio networktemporary identifier (RNTI) monitored by the terminal may be defineddifferently according to the search space. For example, a DCI includinga cyclic redundancy check (CRC) scrambled with a system information RNTI(SI-RNTI), a random access (RA) RNTI (RA-RNTI), a paging-RNTI (P-RNTI),a transmit power control (TPC) PUCCH RNTI (TPC-PUCCH-RNTI), aTPC-PUSCH-RNTI, an enhanced interference management and trafficadaptation (eIMTA) RNTI (eIMTA-RNTI), or the like may be transmittedover the common search space. Since a beamforming is not applied to thecontrol channel (e.g., control signal) in LTE, the common DCI or theUE-specific DCI may be broadcast to multiple terminals via the commonsearch space. Therefore, in LTE, all terminals may acquire the commonDCI or the UE-specific DCI by monitoring the same search space (e.g.,common search space).

On the other hand, in the NR, since a control channel (e.g., controlsignal) may be beamformed, and terminals in the same cell may operate indifferent frequency bands, it may be inappropriate for the terminals tomonitor the same search space to receive a specific common DCI (e.g.,the second common DCI). Therefore, the search space in the NR may bedefined as one integrated search space without being classified into thecommon search space and the UE-specific search space (hereinafterreferred to as ‘Method 400-1’). According to Method 400-1, oneintegrated search space for the terminals may be configured in thecontrol resource set. In this case, a plurality of control resource setsfor the terminal are configured, which means that the same number ofsearch spaces as the number of the plurality of control resource setsare configured.

When the DCI is transmitted through the search space (e.g., integratedsearch space) configured for the terminal, the base station may scramblethe CRC using all types of RNTIs allowed for PDCCH transmission, and theterminal may monitor all type of RNTIs allowed for the PDCCHtransmission in the search space (e.g., integrated search space).Alternatively, the base station may scramble the CRC using an RNTIallowed for the common DCI when transmitting the common DCI through thesearch space in the base control resource set, and scramble the CRCusing all types of RNTIs when transmitting the DCI (e.g., common DCI orUE-specific DCI) through the search space in the additional controlresource set. In this case, the terminal may monitor the RNTI allowedfor the common DCI in the search space in the base control resource set(e.g., common DCI monitoring), and may monitor all types of RNTIs in thesearch space in the additional control resource set (e.g., common DCIand UE-specific DCI monitoring).

When there are many types of RNTIs to be monitored in one search space(e.g., integrated search space), the terminal should perform CRC checksseveral times for a plurality of RNTIs in the blind decoding operationof the PDCCH. In this case, the reception complexity of the terminal mayincrease, but the increase of the reception complexity may be lower thanthe complexity required for decoding the channel. Method 400-1 may beapplied to all control resource sets (e.g., base control resource setand additional control resource sets).

Alternatively, Method 400-1 may be applied only to the additionalcontrol resource sets. When Method 400-1 is applied only to theadditional control resource sets, the common search space and theUE-specific search space may be configured in the base control resourceset. Within the base control resource set, the common search space mayexist by default and the UE-specific search space may be additionallyconfigured. When Method 400-1 is not applied, at least one of the commonsearch space and the UE-specific search space may be configured in theadditional control resource set.

The search space may be predefined for each CCE aggregation level. Forexample, the search space where the terminal performs monitoring (e.g.,the number of PDCCH candidates, the resource location, etc.) may bepredefined at each of the CCE aggregation levels 1, 2, 4 and 8.Alternatively, the search space may be configured by the base station bythe CCE aggregation level, and the base station may inform the terminalof the configured search space. In order to reduce the complexity of thePDCCH decoding operation of the terminal in the NR, the base station mayinform the terminal of the number of PDCCH candidates for each CCEaggregation level or the total number of PDCCH candidates through asignaling procedure. The terminal may perform the PDCCH blind decodingoperation based on the information obtained through the signalingprocedure.

Here, the search space may indicate a sum of search spaces for therespective CCE aggregation levels. Also, the search space may indicateeach search space according to each CCE aggregation level. For example,when the common search space includes search spaces corresponding to theCCE aggregation levels 4 and 8, the corresponding search spaces may bereferred to as one search space. Also, the presence of the plurality ofsearch spaces may indicate that there are a plurality of search spacescorresponding to a plurality of CCE aggregation levels.

Meanwhile, the search space in the control resource set may be definedas follows. The basic unit for the configuration of the control resourceset may be an REG, and there may be CCEs each of which is composed of aplurality of REGs in the control resource set. The CCEs within a singlecontrol resource set may not be overlapped with each other. The searchspace in the control resource set may include REGs. A candidate set ofREGs for defining a specific search space may be referred to as an ‘REGPool’. A REG pool for the common search space may be referred to as a‘common REG pool’, and a REG pool for the UE-specific search space maybe referred to as a ‘UE-specific REG pool’. The search space may beconfigured within the REG pool according to a predefined rule. Forexample, the search space may consist of all the REGs belonging to theREG pool, or may be composed of some REGs belonging to the REG pool. Forexample, in order to configure the search space with some REGs in theREG pool, a hash function used for configuring the search space of thePDCCH or EPDCCH of the LTE may be used identically or similarly.

The REG pool may occupy the entire frequency region of the controlresource set and may include at least one OFDM symbol among the OFDMsymbols constituting the control resource set (hereinafter referred toas a ‘Method 500-1’). A plurality of REG pools may be configured in onecontrol resource set, whereby one control resource set may include aplurality of different types of search spaces (e.g., common search spaceand UE-specific search space). Alternatively, one control resource setmay include a plurality of search spaces of the same type (e.g., aplurality of UE-specific search spaces).

FIG. 4A is a conceptual diagram illustrating a first embodiment of a REGpool in a control resource set, FIG. 4B is a conceptual diagramillustrating a second embodiment of a REG pool in a control resourceset, FIG. 4C is a conceptual diagram illustrating a third embodiment ofa REG pool in a control resource set, FIG. 4D is a conceptual diagramillustrating a fourth embodiment of a REG pool in a control resourceset, and FIG. 4E is a conceptual diagram illustrating a fifth embodimentof a REG pool in a control resource set.

Referring to FIGS. 4A to 4E, a plurality of search spaces may exist inone control resource set. The control resource set may be configured ina continuous frequency region (e.g., continuous PRBs) or a discontinuousfrequency region (e.g., discontinuous PRBs). According to Method 500-1,each of a first REG pool and a second REG pool may occupy the entirefrequency region of the control resource set. That is, the frequencyregions of the first REG pool and the second REG pool may be the same asthe frequency region of the control resource set.

In FIGS. 4A to 4C, time periods of the control resource set may beperiodically repeated. For example, each time period of the controlresource set may consist of 4 consecutive OFDM symbols. The first REGpool may be a common REG pool, and a common search space may be definedwithin the first REG pool. The second REG pool may be a UE-specific REGpool, and a UE-specific search space may be defined within the secondREG pool. For fast reception of the common DCI, the common REG pool maybe composed of first N OFDM symbols in the control resource set(hereinafter referred to as a ‘Method 500-2’. N may be an integer of 1or more.

The search space configured in the REG pool (e.g., common REG pool) towhich Method 500-2 is applied may be protected so that the search spacecan be monitored by the terminal. The terminal may always monitor thesearch space corresponding to the first REG pool.

In FIG. 4A, the REG pools (e.g., the first REG pool and the second REGpool) may be configured so as to not overlap with each other(hereinafter referred to as a ‘Method 510-1’). According to Method510-1, since there is no resource collision between PDCCH candidates indifferent search spaces, a mapping rule between CCEs and REGs may besimplified.

In FIGS. 4B and 4C, the REG pools (e.g., the first REG pool and thesecond REG pool) may overlap with each other. In FIG. 4B, a part of thefirst REG pool may overlap with the second REG pool (hereinafterreferred to as a ‘Method 510-2’). In FIG. 4C, the first REG pool may beincluded in the second REG pool (hereinafter referred to as a ‘Method510-3’). When Method 510-2 or 510-3 is used, resource efficiency can beimproved compared to Method 510-1. Also, since the REG pool of thesearch space can be extended according to Method 510-2 and Method 510-3,a collision probability between the search spaces of the terminals maybe reduced when different search spaces are defined for the respectiveterminals.

In FIGS. 4D and 4E, the control resource set may include the entire timeresource (i.e., all slots and all OFDM symbols) in the time domain. Forexample, the control resource set may include OFDM symbols #0 to #13 ofall slots. The time periods of each REG pool constituting the controlresource set may have periodicity, and each REG pool may include one ora plurality of consecutive OFDM symbols within one period. In FIG. 4D,the REG pools may have a cycle in units of the slot. The cycle of thefirst REG pool may be one slot and the time period of the first REG poolmay include first and second OFDM symbols (i.e., OFDM symbols #0 and #1)in each period. The cycle of the second REG pool may be 2 slots and thetime period of the second REG pool may include third and fourth OFDMsymbols (i.e., OFDM symbols #2 and #3 of the first slot) in each period.For example, the first REG pool may be a common REG pool, and a commonsearch space may be defined within the first REG pool. For example, thesecond REG pool may be a UE-specific REG pool, and a UE-specific searchspace may be defined within the second REG pool.

In FIG. 4E, some REG pools may have a cycle in units of the slot, andsome REG pools may have a cycle of OFDM symbol units. The cycle of thefirst REG pool may be one slot and the time period of the first REG poolmay include the first OFDM symbol (i.e., OFDM symbol #0) in each period.The cycle of the second REG pool may be 2 OFDM symbols and the timeperiod of the second REG pool may include the first OFDM symbol (e.g.,OFDM symbol #0, #2, #4, #6, #8, #10, or #12) in each period. Accordingto the configuration scheme described above, the first REG pool may beincluded in the second REG pool. For example, a slot-based scheduling(e.g., scheduling for eMBB transmission) may be performed through thesearch space defined within the first REG pool. For example, aminislot-based scheduling (e.g., scheduling for URLLC transmission) maybe performed through the search space defined within the second REGpool.

The configuration information of the REG pool may be transmitted fromthe base station to the terminal through a signaling procedure (e.g.,RRC signaling procedure). The configuration information of the REG poolmay include at least one of time resource information and frequencyresource information of the REG pool. The time resource information ofthe REG pool may include position information of the OFDM symbol(s)constituting the REG pool (e.g., at least one of the length of the timeperiod of the REG pool, the starting point of the time period, and thecycle). Since the PDCCH search space may be defined in the REG pool, thetime resource information of the REG pool may mean information on aperiod during which the terminal monitors the PDCCH search space.

The frequency resource information of the REG pool may not be separatelyconfigured to the terminal according to Method 500-1, and the frequencyresource of the REG pool may be the same as a frequency resource regionof the control resource set including the corresponding REG pool (or, acontrol resource set having a logical relationship with thecorresponding REG pool). For this, when the base station configures theREG pool, the base station may inform the terminal of the controlresource set in which the REG pool is included (or, the control resourceset having a logical relationship with the corresponding REG pool). Forexample, the configuration information of the REG pool may include anidentifier (ID) of the control resource set, and the control resourceset having the ID may be preconfigured in the terminal or configuredtogether with the REG pool.

CCE-REG Mapping Structure

The CCE-REG mapping structure may be defined based on the controlresource set or the REG pool belonging to the control resource set. Whena plurality of control resource sets or their corresponding searchspaces are overlapped on a time-frequency resource, the relationshipbetween search spaces may be considered in the CCE-REG mappingstructure. A distributed mapping scheme may be used for the CCE-REGmapping. The distributed mapping scheme may include a case where theREGs constituting each CCE are located discontinuously in at least oneof the time period and the frequency band. When the distributed mappingscheme is performed, one-dimensional interleaving in units of the OFDMsymbol may be performed.

FIG. 5 is a conceptual diagram illustrating a first embodiment of aCCE-REG mapping scheme.

Referring to FIG. 5, a time period of the control resource set mayinclude 4 OFDM symbols, and 6 REGs may be located in each of 4 OFDMsymbols. The REG index in each of the 4 OFDM symbols may be setsequentially. For example, the REG index may increase as the frequencyband in which the REG is located increases. An REG-level frequencyinterleaving operation may be applied in each of the 4 OFDM symbolsbelonging to the control resource set (hereinafter referred to as a‘Method 600-1’). When the REG-level frequency interleaving operation iscompleted, the REGs in each of the 4 OFDM symbols may be distributed inthe frequency band based on a preconfigured interleaving pattern. Here,the interleaving pattern may be set differently for each OFDM symbol.When the interleaving pattern is a pseudo-random interleaving pattern,the pseudo-random interleaving pattern may be set independently for eachOFDM symbol. When the interleaving pattern has a predetermined rule, theinterleaving patterns between the OFDM symbols may have mutualdependency. As an example, in the same row (e.g., same PRB), the sameREG index may not be duplicated. As another example, the sameinterleaving pattern may be applied to each OFDM symbol.

An REG pool including at least one interleaved REG may be configured inthe control resource set. After the REG pool is configured in thecontrol resource set, the REG index set for each OFDM symbol may betranslated into a global REG index having a unique value in the REG pool(hereinafter referred to as a ‘Method 600-2’).

FIG. 6 is a conceptual diagram illustrating a first embodiment of asearch space configured in an REG pool.

Referring to FIG. 6, a search space may be configured based on Method600-1 and Method 600-2. The REG index in the control resource set ofFIG. 6 may be the same as the REG index (e.g., the REG index after theREG-level frequency interleaving is performed) in the control resourceset of FIG. 5. The REG pool may include 2 OFDM symbols (e.g., OFDMsymbols #0 and #1) of the control resource set, and the REG index of theREG pool may be converted to a global REG index.

For example, the global REG index may be configured first in thefrequency band of the first OFDM symbol of the REG pool, and may beconfigured in the frequency band of the second OFDM symbol of the REGpool after indexing of the first OFDM symbol of the REG pool iscompleted. In this case, the global REG index may be indexed based onthe order of REG indexes in the control resource set. In the first OFDMsymbol of the REG pool, the global REG index m1 may be configured to beequal to the REG index in the control resource set. When the REG indexis configured as (m=0, 1, 2, 3, 4, 5) in the first OFDM symbol in theREG pool, the global REG index m1 in the first OFDM symbol of the REGpool may be configured to be equal to m. In the second OFDM symbol ofthe REG pool, the global REG index m2 may be configured as follows. Whenthe REG index is configured as (m=0, 1, 2, 3, 4, 5) in the second OFDMsymbol of the REG pool and the number of REGs per OFDM symbol is Q(e.g., 6), the global REG index m2 in the OFDM symbol may be configuredbased on (m+Q) (e.g., m+6) (hereinafter, referred to as a ‘Method600-3’).

In the first embodiment of FIG. 6, 2 CCEs (e.g., CCE #0 and CCE #1) maybe configured in the REG pool, and each CCE may include at least one REG(e.g., 4 REGs). The REGs belonging to one CCE may have continuous globalREG indexes. For example, the REGs corresponding to the global REGs #0to #3 may be mapped to the CCE #0, and the REGs corresponding to theglobal REGs #4 to #7 may be mapped to the CCE #1. In this case, the CCE#0 may be distributed in the frequency band within the first OFDMsymbol, and the CCE #1 may be configured in two OFDM symbols. The DCIthat the terminal should receive quickly may be transmitted through theCCE #0. The DCI that has relatively more spare time for processing maybe transmitted through the CCE #1 or an aggregated CCE including the CCE#0 and the CCE #1. The common search space, the UE-specific searchspace, and the integrated search space may be configured based on themethod described with reference to FIG. 6. For example, each of thecommon search space, the UE-specific search space, and the integratedsearch space may include at least one CCE.

FIG. 7 is a conceptual diagram illustrating a second embodiment of asearch space configured in an REG pool.

Referring to FIG. 7, a search space may be configured based on Method600-1 and Method 600-2. The REG index in the control resource set ofFIG. 7 may be the same as the REG index (e.g., the REG index after theREG-level frequency interleaving is performed) in the control resourceset of FIG. 5. The first OFDM symbol (e.g., REGs #0 to #5) of thecontrol resource set and the REGs #0 and #1 in the second OFDM symbol ofthe control resource set may be used for other purposes (e.g., thesearch space illustrated in FIG. 6, and REG used for other physicalchannels and signals). The REG pool may include 3 OFDM symbols (e.g.,OFDM symbols #1 to #3) of the control resource set, and the REG index ofthe REG pool may be converted to a global REG index.

For example, after the indexing operation for the first OFDM symbol ofthe REG pool is completed, the indexing operation may be performed inthe frequency band of the second OFDM symbol of the REG pool, and afterthe indexing operation for the second OFDM symbol of the REG pool iscompleted, the indexing operation may be performed in the frequency bandof the third OFDM symbol of the REG pool. Since the REGs #0 and #1 inthe first OFDM symbol of the REG pool are used for other purpose, theREGs #0 and #1 in the first OFDM symbol of the REG pool may be excludedfrom the search space (e.g., CCE).

When the number of REGs excluded from the search space up to the OFDMsymbol #n (e.g., OFDM symbol #1) of the REG pool is L_(n) (e.g., 2), thenumber of REGs belonging to each OFDM symbol is Q (e.g., 6), and the REGindex in the first OFDM symbol in the REG pool is configured as (m=2, 3,4, 5), the global REG index m1 in the first OFDM symbol of the REG poolmay be configured based on (m+Q(n−1)−L_(n) (i.e., m−2)) (hereinafterreferred to as a ‘Method 600-4’). When the number of REGs excluded fromthe search space up to the OFDM symbol #n (e.g., OFDM symbol #2) of theREG pool is L_(n) (e.g., 2), the number of REGs belonging to each OFDMsymbol is Q (e.g., 6), and the REG index in the first OFDM symbol in theREG pool is configured as (m=0, 1, 2, 3, 4, 5), the global REG index m2in the second OFDM symbol of the REG pool may be configured based on(m+Q(n−1)−L_(n) (i.e., m+4)). When the number of REGs excluded from thesearch space up to the OFDM symbol #n (e.g., OFDM symbol #3) of the REGpool is Ln (e.g., 2), the number of REGs belonging to each OFDM symbolis Q (e.g., 6), and the REG index in the third OFDM symbol in the REGpool is configured as (m=0, 1, 2, 3, 4, 5), the global REG index m3 inthe third OFDM symbol of the REG pool may be configured based on(m+Q(n−1)−L_(n) (i.e., m+10)).

In the second embodiment of FIG. 7, 3 CCEs (e.g., CCE #0, CCE #1, andCCE #2) may be configured in the REG pool, and each CCE may include 4REGs. The REGs belonging to one CCE may have continuous global REGindexes. For example, the REGs corresponding to the global REGs #0 to #3may be mapped to the CCE #0, the REGs corresponding to the global REGs#4 to #7 may be mapped to the CCE #1, and the REGs corresponding to theglobal REGs #8 to #11 may be mapped to the CCE #2.

As an example, in the REG pool, the CCE may be used as a UE-specificsearch space, and REGs (e.g., REGs #0 and #1) not configured as the CCEin the first OFDM symbol of the REG pool may be used as a common searchspace. As another example, in the REG pool, the CCE may be used as acommon search space, and REGs (e.g., REGs #0 and #1) not configured asthe CCE in the first OFDM symbol of the REG pool may be used for PDCCCH.

When there is an REG that is not included in the search space in aspecific OFDM symbol in the REG pool, the REG pool may be composed ofthe remaining REGs other than the corresponding REG. When theinterleaving operation is performed according to Method 600-1, aninterleaving pattern may be defined for the REGs other than thecorresponding REG. For example, the interleaving pattern for the firstOFDM symbol of the REG pool of FIG. 7 may be defined for the remaining 4REGs except the REGs #0 and #1. In this case, the length or size of theinterleaver in the first OFDM symbol of the REG pool may be configuredas 4. Alternatively, the REGs #0 and #1 in the first OFDM symbol of theREG pool may be configured as dummy REGs, and an interleaving pattern(e.g., interleaver of length 6) may be defined for the 2 dummy REGs andthe remaining 4 REGs.

When a common search space and a UE-specific search space coexist in onecontrol resource set, the common search space is the search space (e.g.,CCEs #0 and #1) shown in FIG. 6, and the UE-specific search space is thesearch space (e.g., CCEs #0 to #2) shown in FIG. 7, since the secondOFDM symbol of the control resource set is shared by the two searchspaces, PDCCH candidates of the two search spaces may collide with eachother. However, since the CCE #0 of the UE-specific search space ismapped to REGs other than REGs occupied by the CCE #1 of the commonsearch space according to Method 600-4, a collision between the twosearch spaces (e.g., 2 CCEs) may not occur. Therefore, by reducing thecollision probability between the PDCCH candidates, an effect ofincreasing an effective transmission capacity of the downlink controlregion and improving the PDCCH reception performance can be obtained.

FIG. 8 is a conceptual diagram illustrating a third embodiment of asearch space configured in an REG pool.

Referring to FIG. 8, a search space may be configured based on Method600-1 and Method 600-2. The REG index in the control resource set ofFIG. 8 may be the same as the REG index (e.g., the REG index after theREG-level frequency interleaving is performed) in the control resourceset of FIG. 5. The first OFDM symbol (e.g., REGs #0 to #5) of thecontrol resource set and the REGs #0 and #1 in the second OFDM symbol ofthe control resource set may be used for other purposes (e.g., thesearch space illustrated in FIG. 6, and REG used for other physicalchannels and signals). The REG pool may include 3 OFDM symbols (e.g.,OFDM symbols #1 to #2) of the control resource set, and the REG index ofthe REG pool may be converted to a global REG index.

For example, after the indexing operation for the first OFDM symbol ofthe REG pool is completed, the indexing operation may be performed inthe frequency band of the second OFDM symbol of the REG pool, and afterthe indexing operation for the second OFDM symbol of the REG pool iscompleted, the indexing operation may be performed in the frequency bandof the third OFDM symbol of the REG pool. Although the REGs #0 and #1 inthe first OFDM symbol of the REG pool are used for other purpose, asearch space (e.g., CCE) including all the REGs (e.g., REG #0 to #5) inthe first OFDM symbol of the REG pool may be configured.

Global REG indexes for the REGs #2 to #5 not used for other purposes inthe first OFDM symbol of the REG pool may be configured first, and thenglobal REG indexes for the REGs #0 and #1 used for other purposes in thefirst OFDM symbol may be configured (hereinafter referred to as a‘Method 600-5’). When the number of REGs belonging to each OFDM symbolis Q (e.g., 6), and the REG index in the second OFDM symbol of the REGpool is configured as (m=0, 1, 2, 3, 4, 5), the global REG index m2 inthe second OFDM symbol of the REG pool may be configured based on(m+Q(n−1)) (e.g., m+6). Here, n may indicate an index of an OFDM symbolbelonging to the REG pool. When the number of REGs belonging to eachOFDM symbol is Q (e.g., 6), and the REG index in the third OFDM symbolof the REG pool is configured as (m=0, 1, 2, 3, 4, 5), the global REGindex m3 in the third OFDM symbol of the REG pool may be configuredbased on (m+Q(n−1)) (e.g., m+12). Meanwhile, the CCE #0 shown in FIG. 6described above may be used for transmission of a specific common DCI(e.g., slot configuration information). In this case, the terminal mayreceive the common DCI in the first OFDM symbol of the control resourceset without performing the blind decoding operation. When a plurality ofcommon DCIs are transmitted in one slot, the number of PDCCH candidatesused for the common DCI transmission may increase in proportion to thenumber of common DCIs.

The embodiments shown in FIGS. 6 to 8 may be the CCE-REG mappingstructure based on the distributed mapping scheme, and a CCE-REG mappingstructure based on a localized mapping scheme will be described below.When the local mapping scheme is applied, the REGs constituting the CCEmay be configured to be continuous (e.g., as contiguous as possible) inat least one of the time period and the frequency band. The CCEconfigured on the basis of the localized mapping scheme may be suitablefor a case where the base station transmits DCIs by applying a differentbeamforming to each terminal.

In a frequency band, one control resource set may be composed of M CCEs,and in the frequency band, one CCE may be composed of K PRBs. Here, eachof M and K may be an integer. Each of the CCEs constituting one controlresource set and the PRBs constituting one CCE may be continuous ordiscontinuous in the frequency band. For example, in order to obtain afrequency diversity gain, each of the CCEs and PRBs may be continuous ordiscontinuous in the frequency band, and each of the CCEs and PRBs maybe continuous in the frequency band in order to minimize overhead of theconfiguration information of the control resource set (hereinafterreferred to as a ‘Method 700-1’).

Meanwhile, the control resource set or the REG pool may be composed of NOFDM symbols in a time period, and one CCE may be composed of one OFDMsymbol in a time period. Here, N may be an integer. Therefore, onecontrol resource set or one REG pool may be composed of (M×N) CCEs, andthe (M×N) CCEs may correspond to (M×N×K) PRBs (hereinafter referred toas a ‘Method 700-2’). Each of M, N and K may be set differently for eachcontrol resource set (e.g., base control resource set and additionalcontrol resource set) or REG pool. When a plurality of bandwidth partsare configured in the terminal, each of M, N and K may be setdifferently for each bandwidth part. The candidate values of M, N, and Kmay be defined differently for each of the numerologies shown in Table1.

The size of each of the time period and the frequency band of thecontrol resource set may be configured by the base station, and the basestation may transmit the configuration information of the controlresource set (e.g., the size of the time period, the size of thefrequency band) to the terminal through a signaling procedure. Here, thesignaling procedure may include a physical layer dynamic signalingprocedure (e.g., a DCI transmission procedure), a semi-static signalingprocedure (e.g., an RRC signaling procedure or a broadcasting procedureof system information), or the like. For example, when Method 700-2 isused, the base station may inform the terminal of M and N through thesignaling procedure, and a predetermined value of K may be used.

A search space within the control resource set or the REG pool belongingto the control resource set (hereinafter collectively referred to as a‘control resource set’) may be configured as an entire control resourceset (hereinafter referred to as a ‘Method 710’). Alternatively, in thecontrol resource set, the search space may be configured as a partialregion of the control resource set (hereinafter referred to as a ‘Method720’). The search space may refer to a sum of the search spaces for therespective CCE aggregation levels. Depending on the configuration of thesearch space per CCE aggregation level, Method 710 may be classifiedinto Methods 710-1 to 710-3. In Method 710-1, the sum of the searchspaces for the respective CCE aggregation levels may be the entirecontrol resource set, and in Method 710-2, the search spaces of at leastone CCE aggregation level may be a superset including the search spacesof the remaining CCE aggregation levels. In Method 710-3, the searchspaces for the respective CCE aggregation levels may be a part of thecontrol resource set, and the sum of the search spaces of all CCEaggregation levels may be the entire control resource set.

FIG. 9A is a conceptual diagram illustrating a first embodiment of asearch space in a control resource set, FIG. 9B is a conceptual diagramillustrating a second embodiment of a search space in a control resourceset, FIG. 9C is a conceptual diagram illustrating a third embodiment ofa search space in a control resource set.

Referring to FIGS. 9A to 9C, a control resource set may be composed of 2CCEs in a time period, and may be composed of 8 CCEs in a frequencyband. The CCE indexes may be configured in the frequency band first, andthereafter in the time period. The search space shown in FIG. 9A may beconfigured based on Method 710-1. In FIG. 9A, a search space of the CCEaggregation level (i.e., L) 2 may be composed of 8 PDCCH candidates(e.g., PDCCH candidates #0 to #7), and a sum of the 8 PDCCH candidatesmay be an entire control resource set (e.g., entire REG pool). In FIG.9A, a search space of the CCE aggregation level 4 may be composed of 4PDCCH candidates (e.g., PDCCH candidates #0 to #3), and a sum of the 4PDCCH candidates may be an entire control resource set (e.g., entire REGpool).

The search space shown in FIG. 9B may be configured based on Method710-2. In FIG. 9B, a search space of the CCE aggregation level 2 may becomposed of 4 PDCCH candidates (e.g., PDCCH candidates #0 to #3). InFIG. 9B, a search space of the CCE aggregation level 4 may be composedof 4 PDCCH candidates (e.g., PDCCH candidates #0 to #3), and a sum ofthe 4 PDCCH candidates may be an entire control resource set (e.g.,entire REG pool).

The search space shown in FIG. 9C may be configured based on Method710-3. In FIG. 9C, a search space of the CCE aggregation level 2 may becomposed of 4 PDCCH candidates (e.g., PDCCH candidates #0 to #3), andthe 4 PDCCH candidates may a part of the control resource set (e.g., REGpool). In FIG. 9C, a search space of the CCE aggregation level 4 may becomposed of 2 PDCCH candidates (e.g., PDCCH candidates #0 to #1), and asum of the 2 PDCCH candidates may a part of the control resource set(e.g., REG pool). In FIG. 9C, a sum of the 4 PDCCH candidates accordingto the CCE aggregation level 2 and the 2 PDCCH candidates according tothe CCE aggregation level 4 may be an entire control resource set (e.g.,entire REG pool).

Meanwhile, when the CCE aggregation level L is set to 2^(X), theconstraint of the sizes of the time period and the frequency band of thecontrol resource set may be increased. Here, X may be an integer. Thecontrol resource set may be composed of 2^(Y) CCEs in the frequencyband, and the control resource set may be composed of 2^(Z) CCEs in thetime period (hereinafter referred to as a ‘Method 800-1’). Here, each ofY and Z may be an integer. Alternatively, the control resource set maybe composed of 2^(Y) CCEs in the frequency band, and the controlresource set may be composed of Z CCEs in the time period (hereinafterreferred to as a ‘Method 800-2’). When the control resource set isconfigured based on Method 800-1 or Method 800-2, the CCE-REG mappingrule may be simplified. The control resource set shown in FIGS. 9A to 9Cmay be configured based on Method 800-1. In this case, Y may be 3, and Zmay be 1. Also, the control resource set may be composed of Q PRBs inthe frequency band. Here, Q may be an integer.

FIG. 10A is a conceptual diagram illustrating a first embodiment of CCEsaccording to a localized CCE-REG mapping, FIG. 10B is a conceptualdiagram illustrating a second embodiment of CCEs according to alocalized CCE-REG mapping, and FIG. 10C is a conceptual diagramillustrating a third embodiment of CCEs according to a localized CCE-REGmapping.

Referring to FIGS. 10A to 10C, a REG pool may include 2 OFDM symbols,and 9 REGs (e.g., 9 PRBs) may be configured in each of the 2 OFDMsymbols. One CCE may include 4 REGs. When the number of REGs per OFDMsymbol is Q and the number of REGs per CCE is K, Q may be 9, and K maybe 4. The REG indexes may be configured first in the frequency band, andthen in the time period. When the 4 REGs are mapped to one CCE in theorder of the REG indexes, Q may not be divided by K.

The order of REG indexes (e.g., increasing and decreasing directions) inthe respective OFDM symbols in FIG. 10A may be the same. In FIG. 10A,the CCE #0 may include the REGs #0 to #3, the CCE #1 may include theREGs #4 to #7, and the CCE #2 may include the REGs #8 to #11. The orderof REG indexes (e.g., increasing and decreasing directions) in therespective OFDM symbols in FIG. 10B may be different. For example, theREG indexes in the OFDM symbol #0 may increase as the frequencyincreases, and the REG indexes in the OFDM symbol #1 may increase as thefrequency decreases. In FIG. 10B, the CCE #0 may include the REGs #0 to#3, the CCE #1 may include the REGs #4 to #7, and the CCE #2 may includethe REGs #8 to #11. Due to the difference in the methods of configuringthe REG indexes, the CCE #2 in FIG. 10B may be configured in the morelocalized manner in the frequency band as compared with the CCE #2 inFIG. 10A.

When the DCI is transmitted to the terminal through the CCE #2 in thecontrol resource set, a UE-specific DMRS for the corresponding DCI maybe transmitted through 4 PRBs occupied by the CCE #2 in FIG. 10A, and aUE-specific DMRS for the corresponding DCI may be transmitted via 3 PRBsoccupied by the CCE #2 in FIG. 10B. Therefore, the embodiment shown inFIG. 10B may reduce the DMRS overhead as compared with the embodimentshown in FIG. 10A, and the channel estimation performance of theterminal can be improved since the 3 PRBs are continuous in thefrequency band of FIG. 10B.

In each OFDM symbol in FIG. 10C, one REG that is not divided by 4 among9 REGs may be excluded from the indexing, and a REG to which the REGindex is not set may be excluded from the search space. The order of REGindexes (e.g., increasing and decreasing directions) in the respectiveOFDM symbols in FIG. 10C may be the same. Alternatively, the order ofREG indexes in the respective OFDM symbols in FIG. 10C may be different.In FIG. 10C, each of the CCEs may be configured in one OFDM symbol, andthe CCEs may have a lattice structure. In this case, CCEs located indifferent OFDM symbols may be efficiently aggregated. For example, sincethe CCE #0 and the CCE #2 are mapped to the same frequency band, inorder to receive the PDCCH through the aggregated CCEs #0 and #2, theterminal may perform channel estimation for 4 PRBs (i.e., REGs). On theother hand, when the CCE #0 and the CCE #2 are aggregated in FIG. 10A,the terminal should perform channel estimation on 5 PRBs (i.e., REGs) inorder to receive the PDCCH through aggregated CCEs #0 and #2. Also, whena sum of the remaining REGs not divided by K in the OFDM symbols of oneREG pool is equal to or larger than K, a CCE may be further configuredusing the remaining REGs.

The information indicating the size of the control resource setdescribed above may be one of the parameters (hereinafter referred to as‘configuration parameters’) needed for configuring the control resourceset. Also, the configuration parameters may include a numerology, a DMRStype, a position of a time-frequency resource, a CCE mapping rule, a CCEaggregation level, a transmission mode, the number of DMRS ports,information indicating whether a DMRS is shared between the controlchannel and the data channel, and the like. When the control resourceset is configured by an RRC signaling procedure, the configurationparameters may be uniquely configured in the terminal. When theconfiguration parameters are transmitted over a channel (e.g., PBCH)which comprises limited bits, several combinations of some or all of theconfiguration parameters may be predefined, and one of the combinationsmay be configured in the terminal.

A plurality of control resource sets or a plurality of REG pools mayoverlap in the same resource region. In order to increase the resourceefficiency, the same resource region may be configured as an additionalcontrol resource set for a plurality of terminals. In this case, a partor all of the additional control resource sets of different terminalsmay be overlapped. When the additional control resource set isconfigured by a UE-specific signaling procedure, since the terminalcannot identify an additional control resource set of another terminal,the terminal may not identify whether the additional control resourcesets are overlapped or not.

Meanwhile, when a plurality of control resource sets for one terminalare configured to overlap, an operation of the terminal for theplurality of overlapping control resource sets may be defined. In thiscase, the terminal may perform the monitoring operation in each of theplurality of control resource sets in the same manner as when theplurality of control resource sets are not overlapped. Alternatively,priorities of the plurality of overlapping control resource sets may beconfigured, the terminal may monitor an entire search space of a controlresource set having a high priority, and may monitor a part (e.g., aregion not overlapping among the plurality of control resource sets) ofan entire search space of a control resource set having a low priority.When a base control resource set and an additional control resource setfor one terminal are configured to overlap with each other, the priorityof the basic control resource set may be set higher than that of theadditional control resource set.

Coexistence Between PDCCCH and PDCCH

The PDCCCH may be configured in a control resource set or an REG poolincluded in a control resource set (hereinafter collectively referred toas a ‘control resource set’). Since the PDCCCH may be used for thetransmission of the common DCI, the PDCCCH may be located in a frontregion of the control resource set. For example, the PDCCCH may bedistributed in the frequency band in the first OFDM symbol of thecontrol resource set. The PDCCCH may be arranged similarly to the PCFICHof LTE. The PDCCCH and the search space may be located in one OFDMsymbol. In this case, the search space and the PDCCCH may be configuredas follows.

FIG. 11A is a conceptual diagram illustrating a first embodiment of amethod of configuring a search space and a PDCCCH, FIG. 11B is aconceptual diagram illustrating a second embodiment of a method ofconfiguring a search space and a PDCCCH, FIG. 11C is a conceptualdiagram illustrating a third embodiment of a method of configuring asearch space and a PDCCCH, and FIG. 11D is a conceptual diagramillustrating a fourth embodiment of a method of configuring a searchspace and a PDCCCH.

Referring to FIGS. 11A to 11D, a search space and a PDCCCH may exist inone OFDM symbol. For example, the search space may be configured in theremaining resource region other than the resource region in which thePDCCCH is configured. Here, the CCE-REG mapping structure may beconfigured based on the localized mapping scheme. In FIG. 11A, thePDCCCH may not exist, the REGs #0 to #3 may be mapped to the CCE #0, andthe REGs #4 to #7 may be mapped to the CCE #1.

In FIG. 11B, the PDCCCH may be located in the fourth REG. In this case,indexes may be configured for the REGs other than the fourth REG amongall the REGs, and the search space may be composed of the remainingREGs. In order to match the number of REGs included in the CCE to 4,another REG may be mapped to the CCE #0 instead of the fourth REG. Forexample, the REGs #0 to #3 may be mapped to the CCE #0, and the REGs #4to #7 may be mapped to the CCE #1. Therefore, even when there is anexceptional REG (e.g., REG in which the PDCCCH is configured), thenumber of REGs included in the CCE remains the same, so that the PDCCHcandidates may have uniform performance.

In FIG. 11C, the PDCCCH may be located in the fourth REG. In this case,indexes may be configured for the REGs other than the fourth REG amongall the REGs, and the search space may be composed of the remainingREGs. That is, even when there is an exceptional REG (e.g., REG in whichthe PDCCCH is configured), the CCE-REG mapping scheme may not bechanged. Therefore, the REGs #0 to #2 may be mapped to the CCE #0, andthe REGs #3 to #6 may be mapped to the CCE #1.

Meanwhile, the PDCCCH and the search space may be configured to overlapwith each other. In this case, a puncturing function may be appliedaccording to the priority between the PDCCCH and the search space. Whenthe importance of information transmitted through the PDCCCH is higherthan the importance of information transmitted through the search space,and the PDCCCH and the search space coexist, the search space may bepunctured by the PDCCCH. In FIG. 11D, when the PDCCCH is located in thefourth REG, the fourth REG may be indexed as the ‘REG #3’. When thetransmission of the PDCCCH through the REG #3 and the transmission ofthe PDCCH through the CCE #0 are performed at the same time, the fourthREG in the CCE #0 may be punctured by the PDCCCH. In FIG. 11D, theterminal may estimate that the same CCE-REG mapping is used regardlessof the presence or absence of the PDCCCH. Therefore, the terminal in theRRC_IDLE may determine that the same CCE-REG mapping method is used evenwhen the terminal does not acquire the PDCCCH configuration information,so that the monitoring performance of the PDCCH can be improved.

CCE Aggregation Level

Various CCE aggregation levels may be defined for link adaptivetransmission of the PDCCH. For example, a relatively high CCEaggregation level may be required for a terminal located at a cellboundary, and a relatively low CCE aggregation level may be required fora terminal located at a cell center. Also, a relatively low CCEaggregation level may be required for a terminal receiving a UE-specificDCI, and a relatively high CCE aggregation level may be required for aterminal receiving a common DCI.

Therefore, the base station may configure a CCE aggregation level forthe PDCCH blind decoding operation for each search space, and inform theterminal of the configured CCE aggregation level through a signalingprocedure. The base station may configure a CCE aggregation level for asearch space configured through an additional control resource set, anda CCE aggregation level for a search space configured through a basecontrol resource set may be predefined in the specification. The CCEaggregation level may be configured to 1, 2, 4, 8, or the like. Forhigh-reliability transmission such as URLLC, the CCE aggregation levelmay be set to a value greater than 8 (e.g., 16). In order to improve theresource utilization efficiency, the CCE aggregation level may be set toan even number (e.g., 6, 10, etc.) instead of an exponential value of 2.

Variable Search Space

The control resource set may be configured within a limited specificfrequency region. On the other hand, a frequency region used for datatransmission may be wider than the specific frequency band in which thecontrol resource set is configured. Therefore, an operation frequencyrange of the terminal may be adjusted to reduce the power consumption ofthe terminal. For example, the terminal may perform signal receptionoperations in a reduced bandwidth (e.g., narrow band) to monitor adownlink control channel and may perform data transmission and receptionoperations in an increased bandwidth (e.g., wide band) to transmit andreceive data. Through this, power consumption in an RF module of theterminal may be reduced by lowering an analog-to-digital converter (ADC)sampling rate, a FFT size, or the like in the downlink control channelreception procedure. The time required for the terminal to retune the RFfrequency from the wide band to the narrow band may be referred to as‘T_(W,N)’, and the time required for the terminal to retune the RFfrequency from the narrow band to the wide band may be referred to as‘T_(N,W)’. Each of T_(W,N) and T_(N,W) may be increased when the centerfrequency is changed.

The terminal may change the operation frequency range using an intervalin which no signal is transmitted (e.g., an unscheduled data channel, aTDD guard interval, etc.). Also, a gap may be defined for changing theoperation frequency range of the terminal. The terminal may change theoperation frequency range without performing transmission and receptionof signals in the gap, and may tune the RF module. The gap may beconfigured by an explicit method or an implicit method.

The gap may be comprised of consecutive slots, consecutive minislots, orconsecutive OFDM symbols. Each of T_(W,N) and T_(N,W) may be configuredwithin several to several tens of microseconds. For example, 20 μs maybe needed to adjust the operation frequency range of the terminal. Whenthe subcarrier spacing is 15 kHz, the gap may be set shorter than oneOFDM symbol length because 20 μs corresponds to ⅓ of one OFDM symbollength.

Since a peak data rate and spectral efficiency of the terminal can beimproved as the gap is shorter, T_(W,N), and T_(N,W) may be set shorterthan one OFDM symbol length. The gap used to adjust the operationfrequency range from a wide band to a narrow band may be referred to asa ‘first gap’; and the length of the first gap may be referred to as‘G_(W,N)’. The gap used to adjust the operation frequency range from anarrow band to a wide band may be referred to as a ‘second gap’; and thelength of the second gap may be referred to as ‘G_(N,W)’.

For a sub symbol-level gap (i.e., a gap shorter than the length of oneOFDM symbol) used for adjusting the operation frequency range of theterminal, a short OFDM symbol may be configured according to theincrease of the subcarrier spacing. For example, when the subcarrierspacing is changed from 15 kHz to 30 kHz, the length of one OFDM symbolat the subcarrier spacing 15 kHz corresponds to the length of 2 OFDMsymbols at the subcarrier spacing 30 kHz, so that one of the 2 OFDMsymbols at the subcarrier spacing 30 kHz may be used as the gap, and theother OFDM symbol may be used for transmission and reception of asignal.

Some regions of the time period of the control resource set or the REGpool belonging to the control resource set (hereinafter collectivelyreferred to as ‘control resource set’) may be used as a gap. Here, thecontrol resource set may be configured in the narrow band, and a dataregion (e.g., a resource region of the PDSCH, a resource region of thePUSCH, etc.) may be configured in the narrow band or the wide band. Inthis case, a first gap may be located in the front region of the controlresource set on the time domain, and a second gap may be located on therear region of the control resource set on the time domain.

FIG. 12 is a conceptual diagram illustrating a first embodiment of amethod of configuring a data region and a control region.

Referring to FIG. 12, a narrow band downlink control region (e.g.,control resource set) may be configured in one slot, and a wide banddata region may be configured in one slot. The subcarrier spacing forthe data region may be f0, and one slot may comprise 14 OFDM symbols.The downlink control region may be configured to the OFDM symbols #0 and#1. The subcarrier spacing for the downlink control region may be f1,and f1 may be greater than f0. For example, f1 may be two times f0, andin this case the downlink control region may occupy 4 OFDM symbols.

FIG. 13A is a conceptual diagram illustrating a first embodiment of agap configured in a control region, and FIG. 13B is a conceptual diagramillustrating a second embodiment of a gap configured in a controlregion.

Referring to FIGS. 13A and 13B, a narrow band downlink control region(e.g., control resource set, search space) may be configured, a narrowband or wide data region may be configured, and some of the downlinkcontrol region may be configured as a gap. The subcarrier spacing forthe data region may be f0, and the subcarrier spacing for the downlinkcontrol region may be f1. For example, f1 may be two times f0. In thiscase, one OFDM symbol in the data region may correspond to 2 OFDMsymbols in the downlink control region, and the downlink control regionmay occupy 4 OFDM symbols.

In FIG. 13A, since a scheduled wide band data region (e.g., a PDSCHresource region) is present after the downlink control region, theterminal may retune the operation frequency band to monitor the wideband data region. Thus, the last OFDM symbol in the downlink controlregion may be configured as a gap (e.g., a second gap). That is, whenthe bandwidth of the data region is larger than the bandwidth of thedownlink control region, the last OFDM symbol of the downlink controlregion may be configured as a gap. There may not be a scheduled dataregion (e.g., a PDSCH resource region) in a previous slot of thedownlink control region. In this case, since it is not necessary tomonitor the wide band data region in the previous slot of the downlinkcontrol region, the bandwidth of the terminal may already be configuredto be the narrow band. Alternatively, the bandwidth of the terminal maybe changed from the wide band to the narrow band in the previous slot ofthe downlink control region. Therefore, the first OFDM symbol in thedownlink control region may not be configured as a gap.

In FIG. 13B, since a scheduled wide band data region is present in theprevious slot of the downlink control region, the first OFDM symbol ofthe downlink control region may be configured as a gap (e.g., a firstgap). There may be a narrow band data region scheduled in a slot towhich the down control region belongs. The bandwidth of the data regionlocated in the slot to which the downlink control region belongs may beless than or equal to the bandwidth of the downlink control region.Therefore, the terminal may not retune the operation frequency band tomonitor the narrow band data region.

On the other hand, the base station may notify, to the terminal, gapconfiguration information (e.g., presence of the gap, position of thegap, etc.) through an explicit or implicit signaling procedure. Thepresence and position of the gap may be implicitly configured accordingto the presence of the scheduled data region and the frequency bandoccupied by the scheduled data region in the previous time period or thefollowing time period of the downlink control region. For example, whenthere is a wide band data region (e.g., a data region occupying afrequency region other than the frequency region occupied by thedownlink control region) in the previous time period of the downlinkcontrol region, the terminal may estimate P OFDM symbols from the firstOFDM symbol in the downlink control region as a gap. Also, when there isa wide band data region (e.g., a data region occupying a frequencyregion other than the frequency region occupied by the downlink controlregion) in the subsequent time period of the downlink control region,the terminal may estimate the last Q OFDM symbols of the downlinkcontrol region as a gap.

Each of P and Q may be determined based on the numerology of thedownlink control region. In FIG. 13A, Q may be set to 1, and in FIG.13B, P may be set to 1. Each of P and Q may be configured in theterminal through a higher layer signaling procedure. The terminal mayretune the operation frequency range in the gap, and may not performPDCCH monitoring in the gap. When a part of the search spaces in thecontrol resource set is estimated as the gap, the terminal may perform amonitoring operation in remaining search spaces excluding thecorresponding gap. Here, the search space may be changed dynamicallyaccording to the configuration of the gap.

Meanwhile, the presence and position of the gap may be determined basedon the presence of and the frequency region occupied by a physicalchannel (e.g., physical signal) other than the data region (e.g., PDSCHresource region). The gap may be explicitly defined, or the operation ofthe terminal in the gap may be defined. For example, the terminal maynot perform the blind decoding operation of the PDCCH in the gap, andmay not perform a signal reception procedure in the gap. When ascheduled data region (e.g., PDSCH resource region) is present in atleast one of the previous time period and the subsequent time period ofthe control resource set, the terminal that has not acquired a DCIthrough the control resource set may not receive a data channel. In thiscase, since the base station determines that there is a gap for theterminal and the terminal determines that there is no gap, the terminalmay perform the PDCCH monitoring operation in a wider region. Theabove-described signaling procedure of the gap configuration informationand the estimation procedure of the presence and position of the gap maybe applied irrespective of the subcarrier spacing (e.g., subcarrierspacing of the control resource set and the data region), and may beused for the base control resource set as well as the additional controlresource set.

Also, some resources of the data region may be configured as a gap. Forexample, P OFDM symbols from the first OFDM symbol of the data regionmay be configured as a gap, and the last Q OFDM symbols of the dataregion may be configured as a gap. The signaling procedure of the gapconfiguration information of the data region may be the same as orsimilar to the signaling procedure of the gap configuration informationof the control resource set described above and the estimation procedureof the presence and position of the gap of the data region may be thesame as or similar to the estimation procedure of the presence andposition of the gap of the control resource set described above. Forexample, the presence and position of the gap in the data region may beconfigured according to the presence of the scheduled data region andfrequency resources occupied by the scheduled data region in theprevious time period or the subsequent time period of the downlinkcontrol region. Also, the gap may be configured in both the downlinkcontrol region and the data region.

Method of Transmitting a Data Channel in a Control Resource Set

The payload size and the number of DCIs transmitted in each monitoringperiod of a search space configured in a control resource set or a REGpool belonging to the control resource set (hereinafter collectivelyreferred to as a ‘control resource set’) may be different. When thecontrol resource set and the search space corresponding thereto aresemi-statically configured, the resources configured as the controlresource set in a specific time period may be wasted. Therefore, notonly control information but also a data channel may be transmitted inthe control resource set.

FIG. 14 is a conceptual diagram illustrating a first embodiment of adata channel scheduling method.

Referring to FIG. 14, a subcarrier spacing of the control resource setmay be equal to a subcarrier spacing of the data channel (e.g., PDSCH),and the base station may transmit a DCI including scheduling informationof the data channel to the terminal through the control resource set.The combination of the resource regions scheduled by the DCI may beconfigured variously. For example, resource regions (B+E) (e.g., aresource region located outside the time period in which the controlresource set is located) may be scheduled by the DCI. In order toimprove resource efficiency, a resource region (e.g., resource region A,resource region C, resource region D, etc.) within the time period inwhich the control resource set is located may be scheduled by the DCI.

When resource regions (C+D+E) are scheduled by the DCI, the DCI and thedata channel may be transmitted in a frequency division multiplexing(FDM) manner. When resource regions (A+B) or resource regions (A+B+D+E)are scheduled by the DCI, the DCI and the data channel may betransmitted in a TDM manner. When resource regions (D+E) are scheduledby the DCI, a time-frequency resource occupied by the DCI may bedifferent from a time-frequency resource occupied by the data channel.Each of the resource regions A, B, C, D, and E may be configured with atleast one PRB, and the base station may transmit scheduling information(e.g., the number of PRBs included in the data channel, the position ofthe starting OFDM symbol of the data channel, etc.) of the data channel(e.g., data channel configured as a combination of resource regions) tothe terminal through a signaling procedure.

For example, the base station may transmit to the terminal a DCIincluding information indicating the position of the starting OFDMsymbol of the data channel. Here, the DCI may be a UE-specific DCIincluding the scheduling information of the data channel. That is, thecorresponding DCI format may include a CRC scrambled with a C-RNTI. Theinformation indicating the position of the starting OFDM symbol of thedata channel may be an index in a slot or a minislot of the startingOFDM symbol of the data channel, an offset (hereinafter referred to as a‘symbol offset’) between the starting OFDM symbol of the data channeland any one OFDM symbol among the OFDM symbols in which the DCI istransmitted, or the like. The method in which the position of thestarting OFDM symbol of the data channel is indicated by the index inthe slot or minislot of the starting OFDM symbol of the data channel maybe referred to as ‘Method 900-1’, and the method in which the positionof the starting OFDM symbol of the data channel is indicated by thesymbol offset may be referred to as ‘Method 900-2’.

In Method 900-1, when a slot is composed of N OFDM symbols, the index inthe slot of the OFDM symbol may be one of values from 0 to N−1. InMethod 900-1, when a minislot is composed of M OFDM symbols, the indexin the minislot of the OFDM symbol may be one of values from 0 to M−1.In Method 900-2, any one OFDM symbol among the OFDM symbol(s) in whichthe DCI is transmitted may be a first OFDM symbol, a last OFDM symbol,an OFDM symbol immediately following the last OFDM symbol, or the likeamong the OFDM symbol(s) in which the DCI is transmitted. In Method900-2, the offset between OFDM symbols may mean a difference between thetime domain indices of the OFDM symbols.

On the other hand, the subcarrier spacing of the control resource setmay be configured to be different from the subcarrier spacing of thedata channel. In this case, a numerology used to indicate the positionof the starting OFDM symbol of the data channel may be defined.

FIG. 15 is a conceptual diagram illustrating a second embodiment of adata channel scheduling method.

Referring to FIG. 15, the subcarrier spacing of the DCI (i.e., thecontrol channel over which the DCI is transmitted) may be configured tobe different from the subcarrier spacing of the data channel (e.g.,PDSCH). The subcarrier spacing of the data channel may be f0. In thiscase, a first data channel may start at the OFDM symbol #1, a seconddata channel may start at the OFDM symbol #2, and a third data channelmay start at the OFDM symbol #0. The subcarrier spacing of the DCIincluding the scheduling information of the data channel may be set tof1. In this case, the DCI may be transmitted in the OFDM symbol #1.Here, f1 may be greater than f0, and one OFDM symbol at f0 maycorrespond to 2 OFDM symbols at f1. For example, f0 may be 15 kHz, f1may be 30 kHz, and the same CP overhead may be applied to f0 and f1.

The base station may transmit a DCI including information indicating theOFDM symbols #1, #2 and #0 of f0 to the terminal in order to schedulethe data channel. Alternatively, an index of the OFDM symbol (e.g., OFDMsymbol #1) of f1 in which the DCI is transmitted may be translated intoan OFDM symbol index of f0 (e.g., OFDM symbol #0). For example, when theOFDM symbol index of f1 is N1 and the OFDM symbol index of f0corresponding to N1 is N0, an equation N0=floor (N1/(f1/f0)) may bedefined. The base station may transmit a DCI including a symbol offsetindicating the difference between the translated OFDM symbol index ofthe DCI and the starting OFDM symbol index of the data channel to theterminal. In the second embodiment of FIG. 15, the symbol offset mayindicate 1, 2, and 0.

When the data channel is scheduled in multiple slots by a DCI, Methods900-1 and 900-2 may be used. The position of the starting OFDM symbol ofthe data channel may be set equal in each of the slots in which the datachannel is scheduled. When a control resource set located in a specificslot is configured as a zero-power control resource set described below,the data channel may be transmitted by being rate-matched to the controlresource set in the corresponding slot. Also, when the data channel iscross-slot-scheduled by a DCI, Methods 900-1 and 900-2 may be used.Here, the starting OFDM symbol of the data channel may be a specificOFDM symbol in the slot in which the data channel is scheduled.

Meanwhile, in Method 900-1 and Method 900-2, candidates of the startingOFDM symbol of the data channel may be configured in the terminal by ahigher layer signaling procedure (e.g., RRC signaling procedure). Forexample, the base station may inform the terminal of the candidates ofthe starting OFDM symbol of the data channel through a higher layersignaling procedure, and transmit to the terminal a DCI indicating acandidate of the starting OFDM symbol among the candidates of thestarting OFDM symbol configured by the higher layer signaling procedure.When the candidates of the starting OFDM symbol of the data channelconfigured by the higher layer signaling procedure are only one, thecandidate of the starting OFDM symbol of the corresponding data channelmay not be dynamically indicated by the DCI, but may be usedsemi-statically as the starting OFDM symbol of the data channel.

When the data channel allocated to the terminal includes discontinuousOFDM symbols in the time domain, the resource region of the data channelmay be represented by a set of OFDM symbols to which the data channel ismapped. In this case, the starting OFDM symbol of the data channel mayindicate the first OFDM symbol among the OFDM symbols to which the datachannel is mapped.

Methods 900-1 and 900-2 may be used for slot-based data channelscheduling. When one slot includes 14 OFDM symbols (e.g., OFDM symbols#0 to #13) and Method 900-1 is used, the index candidates in the slot ofthe starting OFDM symbol of the data channel are OFDM Symbols #0 to #13.On the other hand, when Method 900-2 is used, the starting OFDM symbolof the data channel is indicated by the offset between the last OFDMsymbol and the starting OFDM symbol of the data channel among the OFDMsymbol (s) in which DCI is transmitted, the candidates of the symboloffset may be −K to (13−K). Here, K may be the index in the slot of thelast OFDM symbol among the OFDM symbol(s) in which the DCI istransmitted. For example, when the DCI is transmitted in the OFDMsymbols #2 and #3, the candidate of the starting OFDM symbol may bebetween −3 and 10.

Methods 900-1 and 900-2 may be used for minislot-based data channelscheduling. The minislot-based data channel scheduling may be performedbased on two methods. In the first method, the base station mayexplicitly inform the terminal of configuration information of aminislot.

FIG. 16 is a conceptual diagram illustrating a third embodiment of adata channel scheduling method.

Referring to FIG. 16, one slot may comprise 14 OFDM symbols, and oneminislot may comprise 2 OFDM symbols. In this case, configurationinformation of the minislot transmitted to the terminal may indicatethat 7 minislots each of which comprises 2 OFDM symbols are configuredin one slot. The OFDM symbol indexes within each minislot may be definedas #0 and #1.

The OFDM symbol index in the minislot may be used for configuring thePDCCH monitoring period and cycle. In the third embodiment of FIG. 16,the base station may inform the terminal that the control resource setor the search space is located in the OFDM symbol #0 in each minislotand that the monitoring period for the search space corresponds to 2OFDM symbols (i.e., minislot length). Also, according to Method 900-1,the base station may inform the terminal of the starting OFDM symbol ofthe data channel using the OFDM symbol index in the minislot.

Referring to FIG. 16, according to Method 900-1, in the minislot #1, theDCI may indicate that the starting OFDM symbol of the data channelcorresponds to the OFDM symbol index #1 in the same minislot (i.e.,minislot #1). In the minislot #4, the DCI may indicate that the startingOFDM symbol of the data channel corresponds to the OFDM symbol index #0in the same minislot (i.e., minislot #4). In this case, in the minislot#4, the data channel may be rate-matched to the control resource set. Inthe minislot #6, the DCI may indicate that the starting OFDM symbol ofthe data channel corresponds to the OFDM symbol index #0 in the sameminislot (i.e., minislot #6). In this case, in the minislot #6, the datachannel may be rate-matched to the DCI.

On the other hand, in the second method of minislot-based data channelscheduling, configuration of the PDCCH monitoring period and time-domainresource allocation of the data channel can be performed in units ofsymbol without explicitly defining or configuring a minislot, so that anequivalent or similar effect as the method based on an explicit minislotcan be provided.

FIG. 17 is a conceptual diagram illustrating a fourth embodiment of adata channel scheduling method.

Referring to FIG. 17, one slot may comprise 14 OFDM symbols, andconfiguration information of a minislot may not be explicitly signaledto the terminal. Instead, the base station may configure the terminal tomonitor the control resource set or the search space in odd-numberedOFDM symbols (e.g., OFDM symbols #0, #2, #4, #6, #8, #10, and #12). Inthis case, according to Method 900-2, the base station may transmit tothe terminal an offset between one OFDM symbol (e.g., the first OFDMsymbol or the last OFDM symbol) among the OFDM symbol(s) in which theDCI is transmitted and the starting OFDM symbol of the data channelthrough the DCI scheduling the data channel. When the data channel isallocated to the same OFDM symbol position as in the third embodiment ofFIG. 16, the symbol offset may be 0 or 1. The candidate value(s) of thesymbol offset may be predefined in the specification or configured inthe terminal by a higher layer signaling procedure.

For example, when the symbol offset is defined on the basis of the firstOFDM symbol among the OFDM symbol(s) in which the DCI is transmitted andthe symbol offset indicated by the DCI is 0 according to Method 900-2,the terminal may determine that the data channel starts from the firstOFDM symbol among the OFDM symbol(s) in which the DCI is transmitted.For example, the DCI transmitted in the OFDM symbol #6 may include asymbol offset 0 and inform the terminal that the data channel startsfrom the OFDM symbol #6. Also, the DCI transmitted in the OFDM symbol#10 may include a symbol offset 0, and may inform the terminal that thedata channel starts from the OFDM symbol #10. As another example, whenthe symbol offset is defined on the basis of the first OFDM symbol amongthe OFDM symbol(s) in which the DCI is transmitted and the symbol offsetindicated by the DCI is 1 according to Method 900-2, the terminal maydetermine that the data channel starts from the next OFDM symbol of thefirst OFDM symbol among the OFDM symbol(s) in which the DCI istransmitted. For example, the DCI transmitted in the OFDM symbol #2 mayinclude a symbol offset 1 and inform the terminal that the data channelstarts from the OFDM symbol #3.

On the other hand, when the explicit minislot structure is not present,the use of Method 900-1 may be undesirable when the PDCCH monitoringperiod of the terminal is shorter than the slot length. For example,when the minislot-based scheduling described with reference to FIG. 17is performed based on Method 900-1, the DCIs of the symbols #2, #6, and#10 may include information indicating the starting symbols #3, #6, and#10 of the PDSCH, respectively. This may require a greater amount of DCIthan Method 900-2 which indicates either 0 or 1.

Meanwhile, in order to prepare for blockage of a link (e.g., a beam pairlink (BPL)) formed by combining a transmission beam of the base stationand a reception beam of the terminal in a multi-beam scenario, the basestation may transmit the DCI for scheduling one data channel (e.g.,PDSCH) to the terminal multiple times using a plurality of controlchannels (e.g., PDCCHs). In this case, in each of the plurality ofcontrol channels, a resource allocation (e.g., CCE aggregation level), achannel coding rate, a reception beam (e.g., a quasi-co-location (QCL)configuration for spatial reception parameters), or the like may bedifferent. In order to simplify hybrid automatic repeat request (HARQ)process management, the plurality of control channels may be transmittedin the same slot. When the number of reception RF chains of the terminalis small, the plurality of control channels may be transmitted throughdifferent OFDM symbols in the same slot.

FIG. 18 is a conceptual diagram illustrating a first embodiment of ascheduling method in a multi-beam scenario.

Referring to FIG. 18, a plurality of PDCCHs may include a first PDCCHand a second PDCCH, the first PDCCH may be transmitted through a firstcontrol resource set located in the OFDM symbol #0 or a first searchspace formed in a first REG pool, and the second PDCCH may betransmitted through a second control resource set located in the OFDMsymbol #1 or a second search space formed in a second REG pool. Theterminal may receive scheduling information for the same data channel(e.g., PDSCH) through the first PDCCH and the second PDCCH. When the DCIincludes information indicating the index in the slot of the startingOFDM symbol of the data channel (e.g., PDSCH) according to Method 900-1,the DCI transmitted through the first PDCCH and the DCI transmittedthrough the second PDCCH may indicate that the OFDM symbol index #2corresponds to the starting OFDM symbol of the data channel. In thiscase, the payload of the DCI transmitted through the first PDCCH may bethe same as the payload of the DCI transmitted through the second PDCCH.The terminal may improve the PDCCH reception performance by combiningthe DCI transmitted through the first PDCCH and the DCI transmittedthrough the second PDCCH. On the other hand, when the DCI includes anoffset (i.e., symbol offset) between one OFDM symbol (e.g., the firstOFDM symbol) among the OFDM symbol(s) in which the DCI is transmittedand the starting OFDM symbol of the data channel according to Method900-2, the symbol offset indicated by the DCI transmitted through thefirst PDCCH may be 2, and the symbol offset indicated by the DCItransmitted through the second PDCCH may be 1. That is, the symboloffset indicated by each of the first PDCCH and the second PDCCH may bedifferent. In this case, the payload of the DCI transmitted through thefirst PDCCH may be different from the payload of the DCI transmittedthrough the second PDCCH. It may be difficult for the terminal tocombine and receive the DCI transmitted through the first PDCCH and theDCI transmitted through the second PDCCH.

On the other hand, when the candidates of the starting OFDM symbol ofthe data channel are configured by a higher layer signaling and one ofthe candidates of the starting OFDM symbol is indicated by the DCI, theDCI may include a field (hereinafter referred to as a ‘symbol indicationfield’) indicating the starting OFDM symbol of the data channel. Thesymbol indication field may include only information on the startingOFDM symbol of the data channel, and may further include otherinformation besides the information on the starting OFDM symbol of thedata channel. For example, the symbol indication field may furtherinclude an offset between the slot in which the DCI is transmitted andthe slot in which the data channel is transmitted, the length of thetime period of the data channel (e.g., the number of OFDM symbols), thetime-domain position information of the DMRS for decoding the datachannel, and the like.

The size of the symbol indication field (e.g., the number of bits) maybe configured in the terminal by a higher layer signaling, or determinedbased on the number of candidates of the starting OFDM symbol of thedata channel configured by a higher layer signaling. For example, if thenumber of candidates of the starting OFDM symbol of the data channel isP, the number of bits of the symbol indication field may be determinedas ceil(log₂(P)). Here, ceil(x) is a function that outputs the minimumvalue among integers greater than or equal to x. When the symbolindication field further includes other information besides the startingOFDM symbol of the data channel, combination(s) of the candidates of thestarting OFDM symbol of the data channel and the candidates of otherinformation may be set in the terminal by a higher layer signaling, andin this case, the size of the symbol indication field may be determinedby the number of the combinations of the candidates of the starting OFDMsymbol of the data channel and the candidates of other informationconfigured by the higher layer signaling. For example, when the numberof combinations is S, the number of bits of the symbol indication fieldmay be set to ceil(log₂(S)). When the symbol indication field includesat least the information on the starting OFDM symbol of the data channeland the length of the time period of the data channel, and thecandidates of the starting OFDM symbol of the data channel and thecandidates of the length of the time period of the data channel aretransmitted through the higher layer signaling, the candidates of thestarting OFDM symbol and the length of the time period may be jointlyencoded in order to configure various candidate combinations withminimal signaling overhead. For example, the candidate of the startingOFDM symbol of the data channel and the candidate of the length of thetime period of the data channel may correspond to one indicator value inone-to-one manner according to a specific rule, and the indicator valuemay be configured in the terminal by a higher layer signaling.Alternatively, the size of the symbol indication field may be predefinedin the specification as a fixed value.

Each of the above-described Methods 900-1 and 900-2 may be suitable fordifferent scenarios. One of Methods 900-1 and 900-2 may be configured tothe terminal through a signaling procedure, and the starting OFDM symbolof the data channel may be dynamically indicated to the terminal by themethod configured in accordance with the signaling procedure. Here, thesignaling procedure may include a physical layer signaling procedure(e.g., a DCI transmission procedure), a MAC signaling procedure, an RRCsignaling procedure, and the like. The signaling procedure may beperformed explicitly or implicitly.

When the signaling procedure is explicitly performed, the terminal maybe configured to use only one of Methods 900-1 and 900-2. Alternatively,Methods 900-1 and 900-2 may be configured together in the terminal. Forexample, the terminal may be configured to use one of Methods 900-1 and900-2 for each carrier or each bandwidth part. Alternatively, theterminal may be configured to use one of Methods 900-1 and 900-2 foreach control resource set or search space.

When the signaling procedure is implicitly performed, one of Methods900-1 and 900-2 may be configured by setting the time-domain positioninformation of the DMRS for decoding the data channel. For example, theterminal may assume that Method 900-1 is used when the first OFDM symbolto which the DMRS for decoding the data channel is mapped is set to aspecific OFDM symbol (e.g., the third or fourth OFDM symbol) of theslot. Also, the terminal may assume that Method 900-2 is used when thefirst OFDM symbol to which the DMRS for decoding the data channel ismapped is set to a specific OFDM symbol (e.g., the first OFDM symbol) ofthe data channel.

Alternatively, when the signaling procedure is implicitly performed, oneof Methods 900-1 and 900-2 may be configured by setting a monitoringperiod of the control resource set or the search space. For example,when the monitoring period of the control resource set or the searchspace is configured in units of the slot (e.g., one or more slots), theterminal may assume that Method 900-1 is used for the data channelscheduled through the control resource set or the search space. Also,when the monitoring period of the control resource set or the searchspace is configured in units of the symbol (e.g., less than one slot),the terminal may assume that Method 900-2 is used for the data channelscheduled through the control resource set or the search space.

Meanwhile, the base station may configure at least one bandwidth partfor the terminal, and inform the terminal through a signaling procedureof the information on the at least one configured bandwidth part. Thebandwidth part may be a set of consecutive PRBs, and at least one PRB inthe bandwidth part may be used as a data channel (e.g., PDSCH or PUSCH).The terminal may be configured to have a downlink bandwidth part and anuplink bandwidth part, respectively. Different bandwidth parts may beconfigured according to application services supported by the terminal.For example, a first bandwidth part may be configured for the eMBBservice, and a second bandwidth part may be configured for the URLLCservice. In this case, the terminal may transmit or receive an eMBBservice related signal through the first bandwidth part and an URLLCservice related signal through the second bandwidth part.

A plurality of bandwidth parts configured for the same terminal ordifferent terminals may overlap each other. When the plurality ofbandwidth parts are configured for the terminal, the higher layersignaling procedure for Method 900-1 and Method 900-2 may be performedfor each bandwidth part. For example, a large number of candidates forthe starting OFDM symbol of the data channel may be configured for theslot-based data channel scheduling within the first bandwidth part, anda small number of candidates for the starting OFDM symbol of the datachannel may be configured for the minislot-based data channel schedulingwithin the second bandwidth part.

The size of the symbol indication field of the DCI may be different foreach bandwidth part in which the corresponding DCI is transmitted. Inthe case of the above-described embodiment, the size of the DCI symbolindication field of the first bandwidth part may be larger than the sizeof the DCI symbol indication field of the second bandwidth part. Thehigher layer signaling procedure may be configured for each controlresource set or search space. When a plurality of search spaces areconfigured for the terminal, the terminal may be configured with a setof candidates of the starting OFDM symbol of the data channel throughthe higher layer signaling procedure in each of the plurality of searchspaces.

The Methods 900-1 and 900-2 described above may be used for schedulinguplink data channels (e.g., PUSCHs) as well as scheduling downlink datachannels (e.g., PDSCHs). For example, in the downlink transmissionprocedure in which each of Methods 900-1 and 900-2 is applied, thesignaling method may be applied to the uplink transmission procedure.Here, the DCI including uplink scheduling information may be used.

Zero Power Control Resource Set

The base station may configure a zero power control resource set or azero power REG pool (hereinafter collectively referred to as a ‘zeropower control resource set’), and inform the terminal of the configuredzero power control resource sets through a signaling procedure. The zeropower control resource set may indicate a control resource set in whicha search space is not defined or configured. The terminal may not expectthat a PDCCH for itself is transmitted in the zero power controlresource set. Therefore, the terminal may not perform a PDCCH monitoringwithin the zero power control resource set.

When the control resource set is configured in the UE-specific manner,control resource sets configured for the respective plurality ofterminals may occupy independent resource regions. In this case, a zeropower control resource set may be configured to protect the transmissionof control resource sets of other terminals. When a resource region of ascheduled data channel (e.g., PDSCH) includes at least a part of thezero power control resource set configured for the terminal, theterminal may receive the corresponding data channel by rate-matching thedata channel around the zero power control resource set. That is, theterminal may determine that the data channel is transmitted through theremaining resource region excluding the zero power control resource set.Also, when the zero power control resource set is used for rate matchingof the data channel, the terminal may be configured to monitor the DCIin the zero power control resource set. Alternatively, for the terminal,the control resource set configured for the DCI monitoring may beconfigured to as the zero power control resource set. The terminal maymonitor the DCI in the control resource set configured as the zero powercontrol resource set, and may rate-match the data channel (e.g., PDSCH)to the zero power control resource set. In this case, the base stationmay inform the terminal of the ID of the control resource set configuredas the zero power control resource set through a signaling procedure(e.g., RRC signaling). The ID of the control resource set may beincluded in the configuration information of the control resource set,and the terminal may receive the ID when the control resource set isconfigured from the base station. The signaling procedure forconfiguring the control resource set and the signaling procedure forconfiguring the zero power control resource set may be separated. Whenthe control resource set includes a plurality of REG pools, a zero powerREG pool may be configured for each REG pool for rate matching of thedata channel. The base station may inform the terminal of the ID of theREG pool configured as the zero power REG pool and/or the ID of thecontrol resource set to which the corresponding REG pool belongs througha signaling procedure (e.g., RRC signaling).

Search Space Switching

When a plurality of control resource sets or search spaces formed in thecontrol resource set (collectively referred to as ‘search space’) areconfigured for one terminal, the search space monitored by the terminalmay be dynamically switched (hereinafter referred to as a ‘Method1000’). For example, the base station may configure a plurality ofsearch spaces for the terminal in different frequency bands and switchdynamically the search space monitored by the terminal. Therefore, afrequency diversity gain or a scheduling gain for transmission of thecontrol channel may be obtained.

The search space monitored by the terminal may be explicitly orimplicitly configured or indicated to the terminal. In the method ofexplicitly configuring the search space, the base station may inform theterminal of the search space in slot(s) after the current slot (or slotsconsecutive with the current slot) using a DCI of the current slot(hereinafter referred to as a ‘Method 1000-1’). In the method ofimplicitly configuring the search space, the terminal may monitor thesearch space configured in the frequency region closest to the frequencyregion allocated the data channel in a previous slot (hereinafterreferred to as a ‘Method 1000-2’). Method 1000-2 may be applied when thetransmission quality of the scheduled data channel is good.

In another embodiment of the method of implicitly configuring the searchspace, the base station may configure a plurality of bandwidth parts forthe terminal, and configure a control resource set (or search space) foreach bandwidth part. The terminal may monitor the search spaceconfigured in an active bandwidth part. In this case, the base stationmay dynamically switch the search space monitored by the terminal by animplicit method by dynamically instructing the terminal to switch theactive bandwidth part.

For example, the base station may configure a first bandwidth part and asecond bandwidth part to the terminal, and configure a first searchspace and a second search space in the first bandwidth part and thesecond bandwidth part, respectively. When the first bandwidth part ofthe terminal is active, the terminal may monitor the first search spacelogically associated with the first bandwidth part. In this case, thebase station may dynamically instruct the terminal to deactivate thefirst bandwidth part and activate the second bandwidth part (i.e.,switch the active bandwidth part). By the instruction, the terminal maymonitor (i.e., switch the search space for monitoring) the second searchspace logically associated with the second bandwidth part.

For example, the base station may inform the terminal of a bandwidthpart to be activated in slot(s) after the current slot (or slotsconsecutive with the current slot) using the DCI of the current slot,and the terminal may dynamically switch the current search space to thesearch space corresponding to the corresponding bandwidth part. When theminislot based (i.e., symbol-level) search space monitoring isconsidered, dynamic switching of the search space may be applied withinone slot.

Although the base station instructs the terminal to switch the searchspace through the DCI according to Method 1000-1 or 1000-2, if theterminal does not acquire the corresponding DCI, the terminal maymonitor a wrong search space. In order to address this problem, theterminal may support a fallback operation to monitor a specific searchspace at a specific time resource (e.g., specific slot(s)) regardless ofthe switching instruction for the search space. For example, theterminal may receive the DCI by monitoring a preconfigured search spacefor each preconfigured period and time resource. The preconfiguredsearch space may be a search space corresponding to a specific bandwidthpart (e.g., a default bandwidth part).

Two-Step DCI Transmission Method

The DCI may be transmitted to the terminal through a plurality of steps.For example, a UE-specific DCI including downlink scheduling informationor uplink scheduling information may be transmitted to the terminalthrough two steps. A DCI transmitted through the first step may bereferred to as a ‘first DCI’, and a DCI transmitted through the secondstep may be referred to as a ‘second DCI’.

For example, the first DCI may include resource configurationinformation of a data channel (e.g., PDSCH) and the second DCI mayinclude transmission related information of the data channel (e.g., amodulation and coding scheme (MCS), a redundancy version (RV)), and thelike. The first DCI may be transmitted on a control channel (e.g.,PDCCH) in the control resource set and the second DCI may be transmittedon a part of the resource region of the data channel scheduled by thefirst DCI. In this case, the data channel may be rate-matched to theresource region (e.g., PDCCH) to which the second DCI is transmitted.Alternatively, a part of the resource region through which the secondDCI is transmitted may belong to the control resource set.

According to the two-step DCI transmission method described above, apart of the control information may be offloaded to the data channel.The second DCI and the data channel may share a DMRS. In this case, theterminal may decode the second DCI using the DMRS for the data channel.Here, the same precoding (e.g., beamforming) may be applied to thesecond DCI, the data channel and the DMRS. Alternatively, the samereception beam (e.g., QCL for spatial reception parameters) may beconfigured for the second DCI and the data channel.

FIG. 19 is a conceptual diagram illustrating a first embodiment of abeamforming transmission method, and FIG. 20 is a conceptual diagramillustrating a second embodiment of a beamforming transmission method.

Referring to FIGS. 19 and 20, a control channel (e.g., PDCCH) may betransmitted through a relatively wide beam for high transmissionreliability, and a data channel (e.g., PDSCH) may be transmitted througha relatively narrow beam. When the two-step DCI transmission method isused, the first DCI may be transmitted through a relatively wide beamand the second DCI may be transmitted through the same beam (e.g., arelatively narrow beam) as the data channel.

When the scheduling information of the data channel is transmittedthrough the first DCI and the second DCI, the first DCI is transmittedthrough a beam wider than that of the data channel, and the second DCIis transmitted through the same beam as the data channel, a negativeacknowledgment (NACK) indicating a reception failure of the data channelmay be classified into a first NACK and a second NACK. The first NACKmay indicate a failure to receive the second DCI and the data channel.The report of the first NACK may be interpreted as a discontinuoustransmission (DTX) report for the second DCI. The second NACK mayindicate a successful reception of the second DCI and a receptionfailure of the data channel. When the data channel includes a pluralityof transport blocks, the terminal may transmit the first NACK or thesecond NACK for each of the plurality of transport blocks. When the datachannel includes a plurality of code block groups (CBGs), the terminalmay transmit the first NACK or the second NACK for each of the pluralityof CBGs.

When the first DCI is successfully received, the terminal may transmitthe first NACK or the second NACK to the base station at a predeterminedtime from the reception time of the first DCI. For example, in the casethat the first DCI is received in the slot #n, the terminal may transmitthe ACK, the first NACK or the second NACK to the base station in theslot #(n+K). The ACK may indicate a successful reception of the datachannel. Here, n may be an integer of 0 or more, and K may be an integerof 1 or more.

Even the reception of the first DCI fails, the terminal may transmit thefirst NACK or the second NACK to the base station if the terminal knowsthat the second DCI and the PDSCH are transmitted. For example, evenwhen the first DCI is not received in the slot #n, the terminal maydetermine that the first DCI is transmitted in the slot #n based onspecific information (e.g., downlink association index (DAD) indicatedby a DCI received through a slot after the slot #n.

Meanwhile, in the case that the control channel is transmitted through awide beam, and the second DCI and the data channel are transmittedthrough a narrow beam, a probability of occurrence of the first NACK ishigh when inappropriate beamforming is applied to the second DCI and thedata channel, and a probability of occurrence of the second NACK may behigh when appropriate beamforming is applied to the second DCI and thedata channel but the channel quality is low. Here, an average receptionerror rate (e.g., 1%) of the second DCI may be lower than an averagereception error rate (e.g., 10%) of the data channel.

The base station may receive the first NACK or the second NACK from theterminal, and may manage the beam based on the first NACK or the secondNACK. When the first NACK is received from the terminal, the basestation may interpret that the beam for the data channel is not validand may perform a procedure for switching the beam for the data channel.For example, the base station may transmit a reference signal for beammeasurement to the terminal within a short time from the reception ofthe first NACK, receive beam measurement information based on thereference signal from the terminal, and instruct the terminal to performa beam switching operation based on the beam measurement information.When the second NACK is received from the terminal, the base station mayinterpret that the beam for the data channel is valid and perform a linkadaptation procedure (e.g., MCS adjustment, frequency band change of thedata channel, etc.) instead of the beam management procedure.

When the first NACK and the second NACK are used, a HARQ feedback foreach transport block (or, a code block or a code block group) may becomposed of 2 bits. For example, the ACK may be configured as ‘00’, thefirst NACK may be configured as ‘01’, and the second NACK may beconfigured as ‘10’. Here, ‘11’ may indicate different information or maybe configured as a reserved field. For example, the reserved field maybe configured as trigger information requesting recovery or change ofthe beam used for transmission of the second DCI or the data channel.Alternatively, the reserved field may be configured as DTX informationindicating the reception failure of the first DCI. Alternatively, thereserved field may be used as a third NACK. The third NACK may indicatea reception failure of the second DCI and a successful reception of thedata channel.

The HARQ feedback composed of 1 bit may be classified as ACK or NACK,and the NACK may indicate the first NACK or the second NACK. The NACK(e.g., the first NACK or the second NACK) not indicated by the HARQfeedback may be composed of a separate parameter (e.g., a parameterindicating the validity of the beam for the data channel). The separateparameter may be transmitted to the base station with the HARQ feedback.Alternatively, the separate parameter may be transmitted through asignaling procedure. In this case, the transmission time of the separateparameter may be different from the transmission time of the HARQfeedback.

Whether or not the first NACK and the second NACK are used may beconfigured for each control resource set or search space through ahigher layer signaling procedure (e.g., a broadcast informationtransmission procedure, a UE-specific RRC signaling procedure, etc.).For example, whether to use the first NACK and the second NACK may beconfigured for the UE-specific search space. When the use of the firstNACK and the second NACK is configured semi-statically for each controlresource set or search space, the first NACK or the second NACK may betransmitted as the HARQ feedback of the corresponding DCI.Alternatively, the terminal may transmit HARQ feedback for the controlresource set or the search space configured by the base station amongthe control resource sets or search spaces. Alternatively, the basestation may transmit information indicating whether the first NACK andthe second NACK are used to the terminal through the DCI.

Meanwhile, the 2-step DCI transmission method may be used for schedulingthe uplink data channel (e.g., PUSCH). For example, the first NACK orthe second NACK may be transmitted in the HARQ response for the uplinkdata channel.

The embodiments of the present disclosure may be implemented as programinstructions executable by a variety of computers and recorded on acomputer readable medium. The computer readable medium may include aprogram instruction, a data file, a data structure, or a combinationthereof. The program instructions recorded on the computer readablemedium may be designed and configured specifically for the presentdisclosure or can be publicly known and available to those who areskilled in the field of computer software.

Examples of the computer readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above exemplary hardware device can be configured tooperate as at least one software module in order to perform theembodiments of the present disclosure, and vice versa.

While the embodiments of the present disclosure and their advantageshave been described in detail, it should be understood that variouschanges, substitutions and alterations may be made herein withoutdeparting from the scope of the present disclosure.

What is claimed is:
 1. An operation method performed in a user equipment (UE) in a communication system, the operation method comprising: receiving, from a base station, downlink control information (DCI) including scheduling information of a data channel; determining a resource region of the data channel based on the DCI and information indicating a location of a start symbol of the data channel; and receiving, from the base station, the data channel in the determined resource region, wherein the information indicating the location of the start symbol of the data channel is interpreted as a symbol offset between the start symbol of the data channel and a symbol in which the DCI is transmitted.
 2. The operation method of claim 1, wherein the information indicating the location of the start symbol of the data channel is included in the scheduling information or a radio resource control (RRC) message which is received from the base station.
 3. The operation method of claim 1, wherein the symbol in which the DCI is transmitted is a first symbol among one or more symbols used for transmitting the DCI.
 4. The operation method of claim 1, wherein the DCI is received from the base station in a physical downlink control channel (PDCCH).
 5. The operation method of claim 1, wherein the data channel is a physical downlink shared channel (PDSCH).
 6. The operation method of claim 1, further comprising: receiving, from the base station, a RRC message including configuration information which indicates that the information indicating the location of the start symbol of the data channel is interpreted as the symbol offset.
 7. The operation method, of claim 1, wherein, when a mapping type of a demodulation-reference signal (DM-RS) for the data channel is a first mapping type, the information indicating the location of the start symbol of the data channel is interpreted as the symbol offset.
 8. The operation method, of claim 1, wherein, when the data channel is repeatedly transmitted in a plurality of slots, the resource region of the data channel belonging to a first slot among the plurality of slots is determined based on the symbol offset, and the resource region of the data channel belonging to remaining slot(s) except for the first slot among the plurality of slots is determined to be identical to the resource region of the data channel belonging to the first slot.
 9. An operation method performed in a base station in a communication system, the operation method comprising: transmitting, to a user equipment (UE), downlink control information (DCI) including scheduling information of a data channel; determining a resource region of the data channel based on the DCI and information indicating a location of a start symbol of the data channel; and transmitting, to the UE, the data channel in the determined resource region, wherein the information indicating the location of the start symbol of the data channel is interpreted as a symbol offset between the start symbol of the data channel and a symbol in which the DCI is transmitted.
 10. The operation method of claim 9, wherein the information indicating the location of the start symbol of the data channel is included in the scheduling information or a radio resource control (RRC) message which is transmitted from the base station.
 11. The operation method of claim 9, wherein the symbol in which the DCI is transmitted is a first symbol among one or more symbols used for transmitting the DCI.
 12. The operation method of claim 9, wherein the DCI is transmitted to the UE in a physical downlink control channel (PDCCH).
 13. The operation method of claim 9, wherein the data channel is a physical downlink shared channel (PDSCH).
 14. The operation method of claim 9, further comprising: transmitting, to the UE, a RRC message including configuration information which indicates that the information indicating the location of the start symbol of the data channel is interpreted as the symbol offset.
 15. The operation method, of claim 9, wherein, when a mapping type of a demodulation-reference signal (DM-RS) for the data channel is a first mapping type, the information indicating the location of the start symbol of the data channel is interpreted as the symbol offset.
 16. The operation method, of claim 9, wherein, when the data channel is repeatedly transmitted in a plurality of slots, the resource region of the data channel belonging to a first slot among the plurality of slots is determined based on the symbol offset, and the resource region of the data channel belonging to remaining slot(s) except for the first slot among the plurality of slots is determined to be identical to the resource region of the data channel belonging to the first slot. 